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	$177.90	5.106%	$186.9836	$186.98	$187.00	$187.00
Purchase #2	$65.58	8.720%	$71.2986	$71.30	$71.30	$71.30
Purchase #3	$33.38	11.360%	$37.172	$37.17	$37.15	$37.20
Purchase #4	$99.48	5.438%	$104.8897	$104.89	$104.90	$104.90
Purchase #5	$45.71	11.453%	$50.9452	$50.95	$50.95	$50.90
Purchase #6	$156.34	13.786%	$177.893	$177.89	$177.90	$177.90
Purchase #7	$198.70	13.502%	$225.5285	$225.53	$225.55	$225.50
7 purchase totals =	$777.09		$854.7106	$854.71	$854.75	$854.70