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	$248.72	3.418%	$257.2212	$257.22	$257.20	$257.20
Purchase #2	$214.90	9.417%	$235.1371	$235.14	$235.15	$235.10
Purchase #3	$184.47	6.537%	$196.5288	$196.53	$196.55	$196.50
Purchase #4	$196.80	11.205%	$218.8514	$218.85	$218.85	$218.90
Purchase #5	$225.36	6.578%	$240.1842	$240.18	$240.20	$240.20
Purchase #6	$104.66	12.488%	$117.7299	$117.73	$117.75	$117.70
Purchase #7	$60.61	11.112%	$67.345	$67.35	$67.35	$67.30
7 purchase totals =	$1,235.52		$1,332.9976	$1,333.00	$1,333.05	$1,332.90