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	$54.31	13.404%	$61.5897	$61.59	$61.60	$61.60
Purchase #2	$56.56	6.767%	$60.3874	$60.39	$60.40	$60.40
Purchase #3	$87.35	4.435%	$91.224	$91.22	$91.20	$91.20
Purchase #4	$246.94	3.323%	$255.1458	$255.15	$255.15	$255.10
Purchase #5	$135.27	11.292%	$150.5447	$150.54	$150.55	$150.50
Purchase #6	$10.67	7.869%	$11.5096	$11.51	$11.50	$11.50
Purchase #7	$147.52	5.858%	$156.1617	$156.16	$156.15	$156.20
7 purchase totals =	$738.62		$786.5629	$786.56	$786.55	$786.50