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	$201.72	4.543%	$210.8841	$210.88	$210.90	$210.90
Purchase #2	$50.66	8.419%	$54.9251	$54.93	$54.95	$54.90
Purchase #3	$119.43	6.178%	$126.8084	$126.81	$126.80	$126.80
Purchase #4	$51.67	13.167%	$58.4734	$58.47	$58.45	$58.50
Purchase #5	$61.42	5.662%	$64.8976	$64.90	$64.90	$64.90
Purchase #6	$196.63	13.171%	$222.5281	$222.53	$222.55	$222.50
Purchase #7	$150.71	6.176%	$160.0178	$160.02	$160.00	$160.00
7 purchase totals =	$832.24		$898.5345	$898.54	$898.55	$898.50