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	$14.40	6.235%	$15.2978	$15.30	$15.30	$15.30
Purchase #2	$54.63	8.493%	$59.2697	$59.27	$59.25	$59.30
Purchase #3	$238.61	11.142%	$265.1959	$265.20	$265.20	$265.20
Purchase #4	$53.93	8.126%	$58.3124	$58.31	$58.30	$58.30
Purchase #5	$67.78	7.345%	$72.7584	$72.76	$72.75	$72.80
Purchase #6	$222.56	3.653%	$230.6901	$230.69	$230.70	$230.70
Purchase #7	$80.53	6.362%	$85.6533	$85.65	$85.65	$85.70
7 purchase totals =	$732.44		$787.1776	$787.18	$787.15	$787.30