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	$146.88	3.276%	$151.6918	$151.69	$151.70	$151.70
Purchase #2	$75.52	11.198%	$83.9767	$83.98	$84.00	$84.00
Purchase #3	$57.70	6.145%	$61.2457	$61.25	$61.25	$61.20
Purchase #4	$48.34	4.363%	$50.4491	$50.45	$50.45	$50.40
Purchase #5	$7.34	3.103%	$7.5678	$7.57	$7.55	$7.60
Purchase #6	$56.85	13.557%	$64.5572	$64.56	$64.55	$64.60
Purchase #7	$176.41	4.795%	$184.8689	$184.87	$184.85	$184.90
7 purchase totals =	$569.04		$604.3572	$604.37	$604.35	$604.40