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	$63.58	12.708%	$71.6597	$71.66	$71.65	$71.70
Purchase #2	$29.97	3.629%	$31.0576	$31.06	$31.05	$31.10
Purchase #3	$43.81	4.824%	$45.9234	$45.92	$45.90	$45.90
Purchase #4	$197.65	7.584%	$212.6398	$212.64	$212.65	$212.60
Purchase #5	$11.74	9.809%	$12.8916	$12.89	$12.90	$12.90
Purchase #6	$125.37	9.825%	$137.6876	$137.69	$137.70	$137.70
Purchase #7	$18.94	10.794%	$20.9844	$20.98	$21.00	$21.00
7 purchase totals =	$491.06		$532.8441	$532.84	$532.85	$532.90