Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$188.69	12.317%	$211.9309	$211.93	$211.95	$211.90
Purchase #2	$153.37	12.157%	$172.0152	$172.02	$172.00	$172.00
Purchase #3	$39.75	9.499%	$43.5259	$43.53	$43.55	$43.50
Purchase #4	$65.48	8.496%	$71.0432	$71.04	$71.05	$71.00
Purchase #5	$6.85	12.768%	$7.7246	$7.72	$7.70	$7.70
Purchase #6	$196.38	13.719%	$223.3214	$223.32	$223.30	$223.30
Purchase #7	$215.33	9.291%	$235.3363	$235.34	$235.35	$235.30
7 purchase totals =	$865.85		$964.8975	$964.90	$964.90	$964.70