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	$65.62	10.269%	$72.3585	$72.36	$72.35	$72.40
Purchase #2	$65.84	6.397%	$70.0518	$70.05	$70.05	$70.10
Purchase #3	$131.29	11.355%	$146.198	$146.20	$146.20	$146.20
Purchase #4	$113.55	8.338%	$123.0178	$123.02	$123.00	$123.00
Purchase #5	$68.94	13.714%	$78.3944	$78.39	$78.40	$78.40
Purchase #6	$59.70	3.157%	$61.5847	$61.58	$61.60	$61.60
Purchase #7	$235.71	6.859%	$251.8773	$251.88	$251.90	$251.90
7 purchase totals =	$740.65		$803.4825	$803.48	$803.50	$803.60