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	$52.34	13.784%	$59.5545	$59.55	$59.55	$59.60
Purchase #2	$93.78	13.493%	$106.4337	$106.43	$106.45	$106.40
Purchase #3	$106.67	10.305%	$117.6623	$117.66	$117.65	$117.70
Purchase #4	$240.48	12.157%	$269.7152	$269.72	$269.70	$269.70
Purchase #5	$148.34	9.431%	$162.3299	$162.33	$162.35	$162.30
Purchase #6	$128.76	10.686%	$142.5193	$142.52	$142.50	$142.50
Purchase #7	$183.72	11.847%	$205.4853	$205.49	$205.50	$205.50
7 purchase totals =	$954.09		$1,063.7002	$1,063.70	$1,063.70	$1,063.70