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	$197.64	7.327%	$212.1211	$212.12	$212.10	$212.10
Purchase #2	$128.54	4.852%	$134.7768	$134.78	$134.80	$134.80
Purchase #3	$161.25	4.607%	$168.6788	$168.68	$168.70	$168.70
Purchase #4	$66.25	11.588%	$73.9271	$73.93	$73.95	$73.90
Purchase #5	$12.35	5.572%	$13.0381	$13.04	$13.05	$13.00
Purchase #6	$53.93	10.229%	$59.4465	$59.45	$59.45	$59.40
Purchase #7	$75.40	9.377%	$82.4703	$82.47	$82.45	$82.50
7 purchase totals =	$695.36		$744.4587	$744.47	$744.50	$744.40