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	$72.92	7.113%	$78.1068	$78.11	$78.10	$78.10
Purchase #2	$63.43	9.363%	$69.369	$69.37	$69.35	$69.40
Purchase #3	$69.26	13.476%	$78.5935	$78.59	$78.60	$78.60
Purchase #4	$223.40	10.187%	$246.1578	$246.16	$246.15	$246.20
Purchase #5	$138.91	5.387%	$146.3931	$146.39	$146.40	$146.40
Purchase #6	$173.37	11.403%	$193.1394	$193.14	$193.15	$193.10
Purchase #7	$197.29	11.771%	$220.513	$220.51	$220.50	$220.50
7 purchase totals =	$938.58		$1,032.2726	$1,032.27	$1,032.25	$1,032.30