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	$230.69	3.493%	$238.748	$238.75	$238.75	$238.70
Purchase #2	$197.42	7.167%	$211.5691	$211.57	$211.55	$211.60
Purchase #3	$220.66	5.622%	$233.0655	$233.07	$233.05	$233.10
Purchase #4	$28.99	11.240%	$32.2485	$32.25	$32.25	$32.20
Purchase #5	$45.51	10.389%	$50.238	$50.24	$50.25	$50.20
Purchase #6	$85.69	4.735%	$89.7474	$89.75	$89.75	$89.70
Purchase #7	$59.40	3.408%	$61.4244	$61.42	$61.40	$61.40
7 purchase totals =	$868.36		$917.0409	$917.05	$917.00	$916.90