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	$59.73	13.422%	$67.747	$67.75	$67.75	$67.70
Purchase #2	$77.97	13.567%	$88.5482	$88.55	$88.55	$88.50
Purchase #3	$38.96	6.582%	$41.5243	$41.52	$41.50	$41.50
Purchase #4	$192.85	12.772%	$217.4808	$217.48	$217.50	$217.50
Purchase #5	$57.87	3.438%	$59.8596	$59.86	$59.85	$59.90
Purchase #6	$143.29	10.425%	$158.228	$158.23	$158.25	$158.20
Purchase #7	$28.94	11.842%	$32.3671	$32.37	$32.35	$32.40
7 purchase totals =	$599.61		$665.7550	$665.76	$665.75	$665.70