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	$148.59	3.272%	$153.4519	$153.45	$153.45	$153.50
Purchase #2	$172.72	9.366%	$188.897	$188.90	$188.90	$188.90
Purchase #3	$149.81	10.214%	$165.1116	$165.11	$165.10	$165.10
Purchase #4	$130.29	4.266%	$135.8482	$135.85	$135.85	$135.80
Purchase #5	$42.69	7.615%	$45.9408	$45.94	$45.95	$45.90
Purchase #6	$71.42	9.272%	$78.0421	$78.04	$78.05	$78.00
Purchase #7	$146.26	5.845%	$154.8089	$154.81	$154.80	$154.80
7 purchase totals =	$861.78		$922.1005	$922.10	$922.10	$922.00