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	$222.61	12.639%	$250.7457	$250.75	$250.75	$250.70
Purchase #2	$160.92	7.201%	$172.5078	$172.51	$172.50	$172.50
Purchase #3	$223.83	7.374%	$240.3352	$240.34	$240.35	$240.30
Purchase #4	$153.81	7.352%	$165.1181	$165.12	$165.10	$165.10
Purchase #5	$214.95	5.829%	$227.4794	$227.48	$227.50	$227.50
Purchase #6	$172.93	9.610%	$189.5486	$189.55	$189.55	$189.50
Purchase #7	$138.49	12.254%	$155.4606	$155.46	$155.45	$155.50
7 purchase totals =	$1,287.54		$1,401.1954	$1,401.21	$1,401.20	$1,401.10