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	$173.41	13.412%	$196.6677	$196.67	$196.65	$196.70
Purchase #2	$239.41	10.383%	$264.2679	$264.27	$264.25	$264.30
Purchase #3	$106.53	5.812%	$112.7215	$112.72	$112.70	$112.70
Purchase #4	$11.47	9.410%	$12.5493	$12.55	$12.55	$12.50
Purchase #5	$124.40	13.118%	$140.7188	$140.72	$140.70	$140.70
Purchase #6	$108.53	3.717%	$112.5641	$112.56	$112.55	$112.60
Purchase #7	$229.47	11.197%	$255.1638	$255.16	$255.15	$255.20
7 purchase totals =	$993.22		$1,094.6531	$1,094.65	$1,094.55	$1,094.70