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	$241.95	4.484%	$252.799	$252.80	$252.80	$252.80
Purchase #2	$156.73	8.405%	$169.9032	$169.90	$169.90	$169.90
Purchase #3	$243.41	5.131%	$255.8994	$255.90	$255.90	$255.90
Purchase #4	$89.83	4.539%	$93.9074	$93.91	$93.90	$93.90
Purchase #5	$69.47	12.772%	$78.3427	$78.34	$78.35	$78.30
Purchase #6	$63.82	4.205%	$66.5036	$66.50	$66.50	$66.50
Purchase #7	$147.82	3.585%	$153.1193	$153.12	$153.10	$153.10
7 purchase totals =	$1,013.03		$1,070.4746	$1,070.47	$1,070.45	$1,070.40