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	$10.50	7.662%	$11.3045	$11.30	$11.30	$11.30
Purchase #2	$88.25	9.428%	$96.5702	$96.57	$96.55	$96.60
Purchase #3	$139.86	9.680%	$153.3984	$153.40	$153.40	$153.40
Purchase #4	$247.52	12.852%	$279.3313	$279.33	$279.35	$279.30
Purchase #5	$68.57	9.527%	$75.1027	$75.10	$75.10	$75.10
Purchase #6	$53.46	4.433%	$55.8299	$55.83	$55.85	$55.80
Purchase #7	$54.79	8.446%	$59.4176	$59.42	$59.40	$59.40
7 purchase totals =	$662.95		$730.9546	$730.95	$730.95	$730.90