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	$228.67	7.462%	$245.7334	$245.73	$245.75	$245.70
Purchase #2	$218.90	3.142%	$225.7778	$225.78	$225.80	$225.80
Purchase #3	$99.26	12.411%	$111.5792	$111.58	$111.60	$111.60
Purchase #4	$225.25	11.599%	$251.3767	$251.38	$251.40	$251.40
Purchase #5	$55.37	6.119%	$58.7581	$58.76	$58.75	$58.80
Purchase #6	$29.32	9.874%	$32.2151	$32.22	$32.20	$32.20
Purchase #7	$123.82	11.434%	$137.9776	$137.98	$138.00	$138.00
7 purchase totals =	$980.59		$1,063.4179	$1,063.43	$1,063.50	$1,063.50