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	$226.43	7.377%	$243.1337	$243.13	$243.15	$243.10
Purchase #2	$64.80	4.623%	$67.7957	$67.80	$67.80	$67.80
Purchase #3	$93.69	12.850%	$105.7292	$105.73	$105.75	$105.70
Purchase #4	$150.70	13.413%	$170.9134	$170.91	$170.90	$170.90
Purchase #5	$167.39	13.445%	$189.8956	$189.90	$189.90	$189.90
Purchase #6	$20.33	6.539%	$21.6594	$21.66	$21.65	$21.70
Purchase #7	$245.45	4.493%	$256.4781	$256.48	$256.50	$256.50
7 purchase totals =	$968.79		$1,055.6051	$1,055.61	$1,055.65	$1,055.60