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	$62.50	13.466%	$70.9163	$70.92	$70.90	$70.90
Purchase #2	$50.60	8.139%	$54.7183	$54.72	$54.70	$54.70
Purchase #3	$172.63	7.125%	$184.9299	$184.93	$184.95	$184.90
Purchase #4	$243.54	13.527%	$276.4837	$276.48	$276.50	$276.50
Purchase #5	$106.89	9.123%	$116.6416	$116.64	$116.65	$116.60
Purchase #6	$160.55	11.303%	$178.697	$178.70	$178.70	$178.70
Purchase #7	$59.55	4.646%	$62.3167	$62.32	$62.30	$62.30
7 purchase totals =	$856.26		$944.7035	$944.71	$944.70	$944.60