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	$172.52	4.281%	$179.9056	$179.91	$179.90	$179.90
Purchase #2	$59.82	4.299%	$62.3917	$62.39	$62.40	$62.40
Purchase #3	$39.55	4.365%	$41.2764	$41.28	$41.30	$41.30
Purchase #4	$137.75	4.326%	$143.7091	$143.71	$143.70	$143.70
Purchase #5	$149.94	7.538%	$161.2425	$161.24	$161.25	$161.20
Purchase #6	$146.45	13.188%	$165.7638	$165.76	$165.75	$165.80
Purchase #7	$110.74	3.565%	$114.6879	$114.69	$114.70	$114.70
7 purchase totals =	$816.77		$868.9770	$868.98	$869.00	$869.00