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	$212.31	9.225%	$231.8956	$231.90	$231.90	$231.90
Purchase #2	$155.30	9.676%	$170.3268	$170.33	$170.35	$170.30
Purchase #3	$185.54	5.703%	$196.1213	$196.12	$196.10	$196.10
Purchase #4	$157.46	9.578%	$172.5415	$172.54	$172.55	$172.50
Purchase #5	$77.70	12.209%	$87.1864	$87.19	$87.20	$87.20
Purchase #6	$139.33	7.327%	$149.5387	$149.54	$149.55	$149.50
Purchase #7	$10.72	9.785%	$11.769	$11.77	$11.75	$11.80
7 purchase totals =	$938.36		$1,019.3793	$1,019.39	$1,019.40	$1,019.30