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	$101.48	8.204%	$109.8054	$109.81	$109.80	$109.80
Purchase #2	$190.68	8.306%	$206.5179	$206.52	$206.50	$206.50
Purchase #3	$36.96	13.136%	$41.8151	$41.82	$41.80	$41.80
Purchase #4	$100.48	10.580%	$111.1108	$111.11	$111.10	$111.10
Purchase #5	$143.72	10.727%	$159.1368	$159.14	$159.15	$159.10
Purchase #6	$239.94	10.397%	$264.8866	$264.89	$264.90	$264.90
Purchase #7	$113.82	11.587%	$127.0083	$127.01	$127.00	$127.00
7 purchase totals =	$927.08		$1,020.2809	$1,020.30	$1,020.25	$1,020.20