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	$17.96	7.850%	$19.3699	$19.37	$19.35	$19.40
Purchase #2	$96.44	7.468%	$103.6421	$103.64	$103.65	$103.60
Purchase #3	$208.58	8.192%	$225.6669	$225.67	$225.65	$225.70
Purchase #4	$99.50	11.679%	$111.1206	$111.12	$111.10	$111.10
Purchase #5	$232.86	11.159%	$258.8448	$258.84	$258.85	$258.80
Purchase #6	$113.84	4.654%	$119.1381	$119.14	$119.15	$119.10
Purchase #7	$99.76	13.597%	$113.3244	$113.32	$113.30	$113.30
7 purchase totals =	$868.94		$951.1068	$951.10	$951.05	$951.00