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	$123.76	6.387%	$131.6646	$131.66	$131.65	$131.70
Purchase #2	$49.74	3.560%	$51.5107	$51.51	$51.50	$51.50
Purchase #3	$91.39	4.465%	$95.4706	$95.47	$95.45	$95.50
Purchase #4	$24.98	4.802%	$26.1795	$26.18	$26.20	$26.20
Purchase #5	$107.54	10.772%	$119.1242	$119.12	$119.10	$119.10
Purchase #6	$116.91	5.612%	$123.471	$123.47	$123.45	$123.50
Purchase #7	$60.61	8.282%	$65.6297	$65.63	$65.65	$65.60
7 purchase totals =	$574.93		$613.0503	$613.04	$613.00	$613.10