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	$96.59	9.843%	$106.0974	$106.10	$106.10	$106.10
Purchase #2	$98.30	13.634%	$111.7022	$111.70	$111.70	$111.70
Purchase #3	$52.79	13.119%	$59.7155	$59.72	$59.70	$59.70
Purchase #4	$192.66	10.603%	$213.0877	$213.09	$213.10	$213.10
Purchase #5	$214.30	13.200%	$242.5876	$242.59	$242.60	$242.60
Purchase #6	$195.98	10.623%	$216.799	$216.80	$216.80	$216.80
Purchase #7	$175.96	8.173%	$190.3412	$190.34	$190.35	$190.30
7 purchase totals =	$1,026.58		$1,140.3306	$1,140.34	$1,140.35	$1,140.30