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	$147.67	7.625%	$158.9298	$158.93	$158.95	$158.90
Purchase #2	$75.36	4.589%	$78.8183	$78.82	$78.80	$78.80
Purchase #3	$151.34	3.654%	$156.87	$156.87	$156.85	$156.90
Purchase #4	$150.80	3.301%	$155.7779	$155.78	$155.80	$155.80
Purchase #5	$226.85	11.680%	$253.3461	$253.35	$253.35	$253.30
Purchase #6	$248.75	10.679%	$275.314	$275.31	$275.30	$275.30
Purchase #7	$235.66	9.260%	$257.4821	$257.48	$257.50	$257.50
7 purchase totals =	$1,236.43		$1,336.5382	$1,336.54	$1,336.55	$1,336.50