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	$134.55	12.354%	$151.1723	$151.17	$151.15	$151.20
Purchase #2	$177.94	4.293%	$185.579	$185.58	$185.60	$185.60
Purchase #3	$212.73	7.861%	$229.4527	$229.45	$229.45	$229.50
Purchase #4	$241.36	6.185%	$256.2881	$256.29	$256.30	$256.30
Purchase #5	$84.83	4.122%	$88.3267	$88.33	$88.35	$88.30
Purchase #6	$85.98	10.492%	$95.001	$95.00	$95.00	$95.00
Purchase #7	$31.27	6.523%	$33.3097	$33.31	$33.30	$33.30
7 purchase totals =	$968.66		$1,039.1295	$1,039.13	$1,039.15	$1,039.20