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	$198.76	11.397%	$221.4127	$221.41	$221.40	$221.40
Purchase #2	$50.74	11.364%	$56.5061	$56.51	$56.50	$56.50
Purchase #3	$91.53	3.760%	$94.9715	$94.97	$94.95	$95.00
Purchase #4	$9.92	8.850%	$10.7979	$10.80	$10.80	$10.80
Purchase #5	$65.66	10.340%	$72.4492	$72.45	$72.45	$72.40
Purchase #6	$61.82	7.162%	$66.2475	$66.25	$66.25	$66.20
Purchase #7	$116.75	12.735%	$131.6181	$131.62	$131.60	$131.60
7 purchase totals =	$595.18		$654.0030	$654.01	$653.95	$653.90