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	$175.32	12.105%	$196.5425	$196.54	$196.55	$196.50
Purchase #2	$169.86	10.325%	$187.398	$187.40	$187.40	$187.40
Purchase #3	$107.60	7.858%	$116.0552	$116.06	$116.05	$116.10
Purchase #4	$127.31	10.453%	$140.6177	$140.62	$140.60	$140.60
Purchase #5	$19.81	8.748%	$21.543	$21.54	$21.55	$21.50
Purchase #6	$89.29	6.796%	$95.3581	$95.36	$95.35	$95.40
Purchase #7	$61.42	11.756%	$68.6405	$68.64	$68.65	$68.60
7 purchase totals =	$750.61		$826.1550	$826.16	$826.15	$826.10