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	$249.68	10.134%	$274.9826	$274.98	$275.00	$275.00
Purchase #2	$197.89	9.266%	$216.2265	$216.23	$216.25	$216.20
Purchase #3	$99.72	10.854%	$110.5436	$110.54	$110.55	$110.50
Purchase #4	$104.67	13.186%	$118.4718	$118.47	$118.45	$118.50
Purchase #5	$58.47	4.127%	$60.8831	$60.88	$60.90	$60.90
Purchase #6	$93.55	12.802%	$105.5263	$105.53	$105.55	$105.50
Purchase #7	$147.39	3.500%	$152.5487	$152.55	$152.55	$152.50
7 purchase totals =	$951.37		$1,039.1826	$1,039.18	$1,039.25	$1,039.10