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	$225.47	9.662%	$247.2549	$247.25	$247.25	$247.30
Purchase #2	$89.67	3.426%	$92.7421	$92.74	$92.75	$92.70
Purchase #3	$165.38	4.192%	$172.3127	$172.31	$172.30	$172.30
Purchase #4	$75.38	8.489%	$81.779	$81.78	$81.80	$81.80
Purchase #5	$137.33	8.377%	$148.8341	$148.83	$148.85	$148.80
Purchase #6	$81.27	10.363%	$89.692	$89.69	$89.70	$89.70
Purchase #7	$246.38	11.232%	$274.0534	$274.05	$274.05	$274.10
7 purchase totals =	$1,020.88		$1,106.6682	$1,106.65	$1,106.70	$1,106.70