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	$52.54	10.685%	$58.1539	$58.15	$58.15	$58.20
Purchase #2	$87.31	4.873%	$91.5646	$91.56	$91.55	$91.60
Purchase #3	$229.82	8.813%	$250.074	$250.07	$250.05	$250.10
Purchase #4	$216.96	13.693%	$246.6683	$246.67	$246.65	$246.70
Purchase #5	$165.87	8.681%	$180.2692	$180.27	$180.25	$180.30
Purchase #6	$173.32	13.443%	$196.6194	$196.62	$196.60	$196.60
Purchase #7	$18.92	7.662%	$20.3697	$20.37	$20.35	$20.40
7 purchase totals =	$944.74		$1,043.7191	$1,043.71	$1,043.60	$1,043.90