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	$196.33	13.143%	$222.1337	$222.13	$222.15	$222.10
Purchase #2	$141.64	13.684%	$161.022	$161.02	$161.00	$161.00
Purchase #3	$105.37	10.601%	$116.5403	$116.54	$116.55	$116.50
Purchase #4	$211.49	3.559%	$219.0169	$219.02	$219.00	$219.00
Purchase #5	$88.75	13.592%	$100.8129	$100.81	$100.80	$100.80
Purchase #6	$116.90	4.669%	$122.3581	$122.36	$122.35	$122.40
Purchase #7	$190.49	5.171%	$200.3402	$200.34	$200.35	$200.30
7 purchase totals =	$1,050.97		$1,142.2241	$1,142.22	$1,142.20	$1,142.10