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	$38.25	8.855%	$41.637	$41.64	$41.65	$41.60
Purchase #2	$29.92	11.140%	$33.2531	$33.25	$33.25	$33.30
Purchase #3	$213.65	3.713%	$221.5828	$221.58	$221.60	$221.60
Purchase #4	$34.57	5.811%	$36.5789	$36.58	$36.60	$36.60
Purchase #5	$223.65	8.489%	$242.6356	$242.64	$242.65	$242.60
Purchase #6	$116.38	13.130%	$131.6607	$131.66	$131.65	$131.70
Purchase #7	$86.89	9.464%	$95.1133	$95.11	$95.10	$95.10
7 purchase totals =	$743.31		$802.4614	$802.46	$802.50	$802.50