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	$146.76	13.718%	$166.8925	$166.89	$166.90	$166.90
Purchase #2	$100.42	13.735%	$114.2127	$114.21	$114.20	$114.20
Purchase #3	$123.62	13.149%	$139.8748	$139.87	$139.85	$139.90
Purchase #4	$192.54	12.337%	$216.2937	$216.29	$216.30	$216.30
Purchase #5	$36.33	3.107%	$37.4588	$37.46	$37.45	$37.50
Purchase #6	$184.81	9.176%	$201.7682	$201.77	$201.75	$201.80
Purchase #7	$57.95	13.200%	$65.5994	$65.60	$65.60	$65.60
7 purchase totals =	$842.43		$942.1001	$942.09	$942.05	$942.20