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	$230.26	11.375%	$256.4521	$256.45	$256.45	$256.50
Purchase #2	$89.45	10.822%	$99.1303	$99.13	$99.15	$99.10
Purchase #3	$55.34	6.742%	$59.071	$59.07	$59.05	$59.10
Purchase #4	$242.34	6.583%	$258.2932	$258.29	$258.30	$258.30
Purchase #5	$14.75	3.414%	$15.2536	$15.25	$15.25	$15.30
Purchase #6	$170.27	6.681%	$181.6457	$181.65	$181.65	$181.60
Purchase #7	$98.76	12.387%	$110.9934	$110.99	$111.00	$111.00
7 purchase totals =	$901.17		$980.8393	$980.83	$980.85	$980.90