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	$53.62	12.815%	$60.4914	$60.49	$60.50	$60.50
Purchase #2	$23.49	4.719%	$24.5985	$24.60	$24.60	$24.60
Purchase #3	$40.90	11.717%	$45.6923	$45.69	$45.70	$45.70
Purchase #4	$99.72	7.263%	$106.9627	$106.96	$106.95	$107.00
Purchase #5	$35.56	12.522%	$40.0128	$40.01	$40.00	$40.00
Purchase #6	$87.81	13.434%	$99.6064	$99.61	$99.60	$99.60
Purchase #7	$32.69	4.117%	$34.0358	$34.04	$34.05	$34.00
7 purchase totals =	$373.79		$411.3999	$411.40	$411.40	$411.40