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	$21.88	4.175%	$22.7935	$22.79	$22.80	$22.80
Purchase #2	$116.64	5.586%	$123.1555	$123.16	$123.15	$123.20
Purchase #3	$90.30	10.168%	$99.4817	$99.48	$99.50	$99.50
Purchase #4	$236.76	3.289%	$244.547	$244.55	$244.55	$244.50
Purchase #5	$54.53	5.446%	$57.4997	$57.50	$57.50	$57.50
Purchase #6	$24.29	13.400%	$27.5449	$27.54	$27.55	$27.50
Purchase #7	$119.67	6.728%	$127.7214	$127.72	$127.70	$127.70
7 purchase totals =	$664.07		$702.7437	$702.74	$702.75	$702.70