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	$101.64	5.107%	$106.8308	$106.83	$106.85	$106.80
Purchase #2	$64.47	11.269%	$71.7351	$71.74	$71.75	$71.70
Purchase #3	$66.46	9.125%	$72.5245	$72.52	$72.50	$72.50
Purchase #4	$69.59	10.276%	$76.7411	$76.74	$76.75	$76.70
Purchase #5	$16.71	10.414%	$18.4502	$18.45	$18.45	$18.50
Purchase #6	$243.44	5.438%	$256.6783	$256.68	$256.70	$256.70
Purchase #7	$139.45	9.645%	$152.9	$152.90	$152.90	$152.90
7 purchase totals =	$701.76		$755.8600	$755.86	$755.90	$755.80