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	$194.49	3.309%	$200.9257	$200.93	$200.95	$200.90
Purchase #2	$127.53	3.362%	$131.8176	$131.82	$131.80	$131.80
Purchase #3	$231.58	3.820%	$240.4264	$240.43	$240.45	$240.40
Purchase #4	$160.80	10.537%	$177.7435	$177.74	$177.75	$177.70
Purchase #5	$211.85	8.814%	$230.5225	$230.52	$230.50	$230.50
Purchase #6	$237.42	7.540%	$255.3215	$255.32	$255.30	$255.30
Purchase #7	$238.72	7.428%	$256.4521	$256.45	$256.45	$256.50
7 purchase totals =	$1,402.39		$1,493.2093	$1,493.21	$1,493.20	$1,493.10