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	$212.25	6.554%	$226.1609	$226.16	$226.15	$226.20
Purchase #2	$94.68	11.842%	$105.892	$105.89	$105.90	$105.90
Purchase #3	$238.66	13.161%	$270.07	$270.07	$270.05	$270.10
Purchase #4	$47.78	5.625%	$50.4676	$50.47	$50.45	$50.50
Purchase #5	$96.36	3.694%	$99.9195	$99.92	$99.90	$99.90
Purchase #6	$181.35	5.240%	$190.8527	$190.85	$190.85	$190.90
Purchase #7	$59.70	11.718%	$66.6956	$66.70	$66.70	$66.70
7 purchase totals =	$930.78		$1,010.0583	$1,010.06	$1,010.00	$1,010.20