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	$74.77	13.874%	$85.1436	$85.14	$85.15	$85.10
Purchase #2	$233.53	3.506%	$241.7176	$241.72	$241.70	$241.70
Purchase #3	$241.46	9.454%	$264.2876	$264.29	$264.30	$264.30
Purchase #4	$184.68	6.256%	$196.2336	$196.23	$196.25	$196.20
Purchase #5	$247.86	3.252%	$255.9204	$255.92	$255.90	$255.90
Purchase #6	$28.27	7.681%	$30.4414	$30.44	$30.45	$30.40
Purchase #7	$78.68	11.772%	$87.9422	$87.94	$87.95	$87.90
7 purchase totals =	$1,089.25		$1,161.6864	$1,161.68	$1,161.70	$1,161.50