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	$233.63	4.143%	$243.3093	$243.31	$243.30	$243.30
Purchase #2	$26.47	5.138%	$27.83	$27.83	$27.85	$27.80
Purchase #3	$156.48	11.361%	$174.2577	$174.26	$174.25	$174.30
Purchase #4	$247.82	3.387%	$256.2137	$256.21	$256.20	$256.20
Purchase #5	$177.32	12.727%	$199.8875	$199.89	$199.90	$199.90
Purchase #6	$195.95	10.414%	$216.3562	$216.36	$216.35	$216.40
Purchase #7	$86.56	13.801%	$98.5061	$98.51	$98.50	$98.50
7 purchase totals =	$1,124.23		$1,216.3605	$1,216.37	$1,216.35	$1,216.40