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	$216.37	11.240%	$240.69	$240.69	$240.70	$240.70
Purchase #2	$151.40	6.319%	$160.967	$160.97	$160.95	$161.00
Purchase #3	$143.84	12.170%	$161.3453	$161.35	$161.35	$161.30
Purchase #4	$70.57	3.301%	$72.8995	$72.90	$72.90	$72.90
Purchase #5	$86.83	12.309%	$97.5179	$97.52	$97.50	$97.50
Purchase #6	$60.73	9.709%	$66.6263	$66.63	$66.65	$66.60
Purchase #7	$240.77	8.717%	$261.7579	$261.76	$261.75	$261.80
7 purchase totals =	$970.51		$1,061.8039	$1,061.82	$1,061.80	$1,061.80