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	$125.76	11.760%	$140.5494	$140.55	$140.55	$140.50
Purchase #2	$243.33	4.290%	$253.7689	$253.77	$253.75	$253.80
Purchase #3	$138.72	7.800%	$149.5402	$149.54	$149.55	$149.50
Purchase #4	$146.45	13.231%	$165.8268	$165.83	$165.85	$165.80
Purchase #5	$176.62	8.686%	$191.9612	$191.96	$191.95	$192.00
Purchase #6	$174.27	9.871%	$191.4722	$191.47	$191.45	$191.50
Purchase #7	$17.83	3.325%	$18.4228	$18.42	$18.40	$18.40
7 purchase totals =	$1,022.98		$1,111.5415	$1,111.54	$1,111.50	$1,111.50