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	$167.33	13.456%	$189.8459	$189.85	$189.85	$189.80
Purchase #2	$146.68	3.267%	$151.472	$151.47	$151.45	$151.50
Purchase #3	$99.92	8.489%	$108.4022	$108.40	$108.40	$108.40
Purchase #4	$105.56	13.108%	$119.3968	$119.40	$119.40	$119.40
Purchase #5	$75.82	3.427%	$78.4184	$78.42	$78.40	$78.40
Purchase #6	$97.75	13.672%	$111.1144	$111.11	$111.10	$111.10
Purchase #7	$150.29	8.183%	$162.5882	$162.59	$162.60	$162.60
7 purchase totals =	$843.35		$921.2379	$921.24	$921.20	$921.20