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	$189.42	3.503%	$196.0554	$196.06	$196.05	$196.10
Purchase #2	$33.48	5.383%	$35.2822	$35.28	$35.30	$35.30
Purchase #3	$94.95	11.363%	$105.7392	$105.74	$105.75	$105.70
Purchase #4	$7.46	10.782%	$8.2643	$8.26	$8.25	$8.30
Purchase #5	$90.62	5.401%	$95.5144	$95.51	$95.50	$95.50
Purchase #6	$35.44	4.139%	$36.9069	$36.91	$36.90	$36.90
Purchase #7	$59.43	11.311%	$66.1521	$66.15	$66.15	$66.20
7 purchase totals =	$510.80		$543.9145	$543.91	$543.90	$544.00