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	$151.93	5.434%	$160.1859	$160.19	$160.20	$160.20
Purchase #2	$129.30	12.727%	$145.756	$145.76	$145.75	$145.80
Purchase #3	$152.60	8.277%	$165.2307	$165.23	$165.25	$165.20
Purchase #4	$175.50	11.760%	$196.1388	$196.14	$196.15	$196.10
Purchase #5	$66.57	7.268%	$71.4083	$71.41	$71.40	$71.40
Purchase #6	$104.96	11.176%	$116.6903	$116.69	$116.70	$116.70
Purchase #7	$12.58	5.513%	$13.2735	$13.27	$13.25	$13.30
7 purchase totals =	$793.44		$868.6835	$868.69	$868.70	$868.70