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	$82.42	12.407%	$92.6458	$92.65	$92.65	$92.60
Purchase #2	$159.36	6.180%	$169.2084	$169.21	$169.20	$169.20
Purchase #3	$62.64	5.216%	$65.9073	$65.91	$65.90	$65.90
Purchase #4	$31.33	12.464%	$35.235	$35.24	$35.25	$35.20
Purchase #5	$40.75	5.726%	$43.0833	$43.08	$43.10	$43.10
Purchase #6	$74.25	11.117%	$82.5044	$82.50	$82.50	$82.50
Purchase #7	$200.86	12.382%	$225.7305	$225.73	$225.75	$225.70
7 purchase totals =	$651.61		$714.3147	$714.32	$714.35	$714.20