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	$47.67	11.240%	$53.0281	$53.03	$53.05	$53.00
Purchase #2	$165.85	9.441%	$181.5079	$181.51	$181.50	$181.50
Purchase #3	$62.74	9.688%	$68.8183	$68.82	$68.80	$68.80
Purchase #4	$114.26	11.170%	$127.0228	$127.02	$127.00	$127.00
Purchase #5	$183.25	4.164%	$190.8805	$190.88	$190.90	$190.90
Purchase #6	$171.42	9.175%	$187.1478	$187.15	$187.15	$187.10
Purchase #7	$38.78	3.780%	$40.2459	$40.25	$40.25	$40.20
7 purchase totals =	$783.97		$848.6513	$848.66	$848.65	$848.50