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	$146.88	5.728%	$155.2933	$155.29	$155.30	$155.30
Purchase #2	$176.29	11.278%	$196.172	$196.17	$196.15	$196.20
Purchase #3	$42.85	7.873%	$46.2236	$46.22	$46.20	$46.20
Purchase #4	$101.73	6.294%	$108.1329	$108.13	$108.15	$108.10
Purchase #5	$140.49	10.512%	$155.2583	$155.26	$155.25	$155.30
Purchase #6	$88.29	5.700%	$93.3225	$93.32	$93.30	$93.30
Purchase #7	$219.56	13.108%	$248.3399	$248.34	$248.35	$248.30
7 purchase totals =	$916.09		$1,002.7425	$1,002.73	$1,002.70	$1,002.70