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	$161.29	12.728%	$181.819	$181.82	$181.80	$181.80
Purchase #2	$159.53	8.194%	$172.6019	$172.60	$172.60	$172.60
Purchase #3	$55.98	5.702%	$59.172	$59.17	$59.15	$59.20
Purchase #4	$208.71	11.104%	$231.8852	$231.89	$231.90	$231.90
Purchase #5	$232.84	4.414%	$243.1176	$243.12	$243.10	$243.10
Purchase #6	$158.38	4.761%	$165.9205	$165.92	$165.90	$165.90
Purchase #7	$204.68	5.586%	$216.1134	$216.11	$216.10	$216.10
7 purchase totals =	$1,181.41		$1,270.6296	$1,270.63	$1,270.55	$1,270.60