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	$174.95	9.137%	$190.9352	$190.94	$190.95	$190.90
Purchase #2	$91.97	3.451%	$95.1439	$95.14	$95.15	$95.10
Purchase #3	$74.48	10.260%	$82.1216	$82.12	$82.10	$82.10
Purchase #4	$166.49	13.621%	$189.1676	$189.17	$189.15	$189.20
Purchase #5	$147.92	11.815%	$165.3967	$165.40	$165.40	$165.40
Purchase #6	$94.77	10.572%	$104.7891	$104.79	$104.80	$104.80
Purchase #7	$176.94	12.675%	$199.3671	$199.37	$199.35	$199.40
7 purchase totals =	$927.52		$1,026.9212	$1,026.93	$1,026.90	$1,026.90