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	$158.97	4.493%	$166.1125	$166.11	$166.10	$166.10
Purchase #2	$91.97	9.526%	$100.7311	$100.73	$100.75	$100.70
Purchase #3	$166.70	4.800%	$174.7016	$174.70	$174.70	$174.70
Purchase #4	$35.37	7.849%	$38.1462	$38.15	$38.15	$38.10
Purchase #5	$95.67	10.533%	$105.7469	$105.75	$105.75	$105.70
Purchase #6	$210.64	5.644%	$222.5285	$222.53	$222.55	$222.50
Purchase #7	$45.82	11.316%	$51.005	$51.01	$51.00	$51.00
7 purchase totals =	$805.14		$858.9718	$858.98	$859.00	$858.80