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	$206.91	13.489%	$234.8201	$234.82	$234.80	$234.80
Purchase #2	$206.60	8.243%	$223.63	$223.63	$223.65	$223.60
Purchase #3	$104.64	11.307%	$116.4716	$116.47	$116.45	$116.50
Purchase #4	$33.83	10.753%	$37.4677	$37.47	$37.45	$37.50
Purchase #5	$158.79	11.118%	$176.4443	$176.44	$176.45	$176.40
Purchase #6	$171.57	5.457%	$180.9326	$180.93	$180.95	$180.90
Purchase #7	$38.28	3.170%	$39.4935	$39.49	$39.50	$39.50
7 purchase totals =	$920.62		$1,009.2598	$1,009.25	$1,009.25	$1,009.20