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	$20.87	10.354%	$23.0309	$23.03	$23.05	$23.00
Purchase #2	$104.71	3.434%	$108.3057	$108.31	$108.30	$108.30
Purchase #3	$249.51	5.132%	$262.3149	$262.31	$262.30	$262.30
Purchase #4	$66.66	5.778%	$70.5116	$70.51	$70.50	$70.50
Purchase #5	$247.91	6.615%	$264.3092	$264.31	$264.30	$264.30
Purchase #6	$59.27	3.819%	$61.5335	$61.53	$61.55	$61.50
Purchase #7	$93.46	12.713%	$105.3416	$105.34	$105.35	$105.30
7 purchase totals =	$842.39		$895.3474	$895.34	$895.35	$895.20