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	$243.97	9.726%	$267.6985	$267.70	$267.70	$267.70
Purchase #2	$58.32	6.496%	$62.1085	$62.11	$62.10	$62.10
Purchase #3	$90.42	11.169%	$100.519	$100.52	$100.50	$100.50
Purchase #4	$71.27	7.300%	$76.4727	$76.47	$76.45	$76.50
Purchase #5	$149.51	12.649%	$168.4215	$168.42	$168.40	$168.40
Purchase #6	$151.54	10.570%	$167.5578	$167.56	$167.55	$167.60
Purchase #7	$240.32	11.359%	$267.6179	$267.62	$267.60	$267.60
7 purchase totals =	$1,005.35		$1,110.3959	$1,110.40	$1,110.30	$1,110.40