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	$36.74	11.306%	$40.8938	$40.89	$40.90	$40.90
Purchase #2	$73.52	11.375%	$81.8829	$81.88	$81.90	$81.90
Purchase #3	$57.37	13.815%	$65.2957	$65.30	$65.30	$65.30
Purchase #4	$180.96	10.178%	$199.3781	$199.38	$199.40	$199.40
Purchase #5	$247.34	3.632%	$256.3234	$256.32	$256.30	$256.30
Purchase #6	$195.65	6.656%	$208.6725	$208.67	$208.65	$208.70
Purchase #7	$16.34	13.476%	$18.542	$18.54	$18.55	$18.50
7 purchase totals =	$807.92		$870.9884	$870.98	$871.00	$871.00