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	$114.57	11.482%	$127.7249	$127.72	$127.70	$127.70
Purchase #2	$58.39	13.353%	$66.1868	$66.19	$66.20	$66.20
Purchase #3	$243.84	12.725%	$274.8686	$274.87	$274.85	$274.90
Purchase #4	$74.38	8.108%	$80.4107	$80.41	$80.40	$80.40
Purchase #5	$74.90	5.655%	$79.1356	$79.14	$79.15	$79.10
Purchase #6	$40.96	3.437%	$42.3678	$42.37	$42.35	$42.40
Purchase #7	$18.67	13.441%	$21.1794	$21.18	$21.20	$21.20
7 purchase totals =	$625.71		$691.8738	$691.88	$691.85	$691.90