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	$169.60	12.518%	$190.8305	$190.83	$190.85	$190.80
Purchase #2	$17.71	13.797%	$20.1534	$20.15	$20.15	$20.20
Purchase #3	$36.36	4.474%	$37.9867	$37.99	$38.00	$38.00
Purchase #4	$52.98	5.141%	$55.7037	$55.70	$55.70	$55.70
Purchase #5	$99.34	5.265%	$104.5703	$104.57	$104.55	$104.60
Purchase #6	$97.50	8.601%	$105.886	$105.89	$105.90	$105.90
Purchase #7	$154.45	6.660%	$164.7364	$164.74	$164.75	$164.70
7 purchase totals =	$627.94		$679.8670	$679.87	$679.90	$679.90