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	$192.39	13.596%	$218.5473	$218.55	$218.55	$218.50
Purchase #2	$117.52	8.625%	$127.6561	$127.66	$127.65	$127.70
Purchase #3	$214.51	8.270%	$232.25	$232.25	$232.25	$232.30
Purchase #4	$207.48	4.306%	$216.4141	$216.41	$216.40	$216.40
Purchase #5	$65.29	9.282%	$71.3502	$71.35	$71.35	$71.40
Purchase #6	$155.30	11.738%	$173.5291	$173.53	$173.55	$173.50
Purchase #7	$100.27	3.873%	$104.1535	$104.15	$104.15	$104.20
7 purchase totals =	$1,052.76		$1,143.9003	$1,143.90	$1,143.90	$1,144.00