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	$211.65	3.327%	$218.6916	$218.69	$218.70	$218.70
Purchase #2	$250.74	9.839%	$275.4103	$275.41	$275.40	$275.40
Purchase #3	$109.87	7.698%	$118.3278	$118.33	$118.35	$118.30
Purchase #4	$52.29	10.807%	$57.941	$57.94	$57.95	$57.90
Purchase #5	$75.68	13.391%	$85.8143	$85.81	$85.80	$85.80
Purchase #6	$218.78	13.309%	$247.8974	$247.90	$247.90	$247.90
Purchase #7	$98.50	12.738%	$111.0469	$111.05	$111.05	$111.00
7 purchase totals =	$1,017.51		$1,115.1293	$1,115.13	$1,115.15	$1,115.00