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	$59.55	10.548%	$65.8313	$65.83	$65.85	$65.80
Purchase #2	$37.34	11.585%	$41.6658	$41.67	$41.65	$41.70
Purchase #3	$119.36	4.246%	$124.428	$124.43	$124.45	$124.40
Purchase #4	$76.98	8.412%	$83.4556	$83.46	$83.45	$83.50
Purchase #5	$117.97	10.629%	$130.509	$130.51	$130.50	$130.50
Purchase #6	$50.39	11.465%	$56.1672	$56.17	$56.15	$56.20
Purchase #7	$124.38	3.238%	$128.4074	$128.41	$128.40	$128.40
7 purchase totals =	$585.97		$630.4643	$630.48	$630.45	$630.50