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	$18.61	6.712%	$19.8591	$19.86	$19.85	$19.90
Purchase #2	$149.74	7.174%	$160.4823	$160.48	$160.50	$160.50
Purchase #3	$165.78	11.580%	$184.9773	$184.98	$185.00	$185.00
Purchase #4	$200.50	4.365%	$209.2518	$209.25	$209.25	$209.30
Purchase #5	$85.62	11.208%	$95.2163	$95.22	$95.20	$95.20
Purchase #6	$22.38	5.279%	$23.5614	$23.56	$23.55	$23.60
Purchase #7	$6.89	10.466%	$7.6111	$7.61	$7.60	$7.60
7 purchase totals =	$649.52		$700.9593	$700.96	$700.95	$701.10