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	$120.41	9.490%	$131.8369	$131.84	$131.85	$131.80
Purchase #2	$139.96	9.694%	$153.5277	$153.53	$153.55	$153.50
Purchase #3	$52.56	12.549%	$59.1558	$59.16	$59.15	$59.20
Purchase #4	$189.55	10.526%	$209.502	$209.50	$209.50	$209.50
Purchase #5	$22.56	9.435%	$24.6885	$24.69	$24.70	$24.70
Purchase #6	$244.97	9.861%	$269.1265	$269.13	$269.15	$269.10
Purchase #7	$248.83	9.428%	$272.2897	$272.29	$272.30	$272.30
7 purchase totals =	$1,018.84		$1,120.1271	$1,120.14	$1,120.20	$1,120.10