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	$228.46	12.428%	$256.853	$256.85	$256.85	$256.90
Purchase #2	$247.93	8.669%	$269.4231	$269.42	$269.40	$269.40
Purchase #3	$21.49	11.827%	$24.0316	$24.03	$24.05	$24.00
Purchase #4	$79.97	11.482%	$89.1522	$89.15	$89.15	$89.20
Purchase #5	$240.54	9.221%	$262.7202	$262.72	$262.70	$262.70
Purchase #6	$81.35	9.870%	$89.3792	$89.38	$89.40	$89.40
Purchase #7	$29.82	3.450%	$30.8488	$30.85	$30.85	$30.80
7 purchase totals =	$929.56		$1,022.4081	$1,022.40	$1,022.40	$1,022.40