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	$190.81	9.731%	$209.3777	$209.38	$209.40	$209.40
Purchase #2	$65.64	8.774%	$71.3993	$71.40	$71.40	$71.40
Purchase #3	$155.56	11.420%	$173.325	$173.33	$173.35	$173.30
Purchase #4	$141.80	6.532%	$151.0624	$151.06	$151.05	$151.10
Purchase #5	$14.43	4.791%	$15.1213	$15.12	$15.10	$15.10
Purchase #6	$120.88	4.742%	$126.6121	$126.61	$126.60	$126.60
Purchase #7	$163.94	6.679%	$174.8896	$174.89	$174.90	$174.90
7 purchase totals =	$853.06		$921.7874	$921.79	$921.80	$921.80