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	$149.74	12.305%	$168.1655	$168.17	$168.15	$168.20
Purchase #2	$200.93	10.727%	$222.4838	$222.48	$222.50	$222.50
Purchase #3	$98.66	7.373%	$105.9342	$105.93	$105.95	$105.90
Purchase #4	$147.70	6.650%	$157.5221	$157.52	$157.50	$157.50
Purchase #5	$129.29	6.180%	$137.2801	$137.28	$137.30	$137.30
Purchase #6	$232.51	7.848%	$250.7574	$250.76	$250.75	$250.80
Purchase #7	$112.95	3.157%	$116.5158	$116.52	$116.50	$116.50
7 purchase totals =	$1,071.78		$1,158.6589	$1,158.66	$1,158.65	$1,158.70