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	$171.28	11.330%	$190.686	$190.69	$190.70	$190.70
Purchase #2	$127.57	13.787%	$145.1581	$145.16	$145.15	$145.20
Purchase #3	$78.28	6.526%	$83.3886	$83.39	$83.40	$83.40
Purchase #4	$166.78	6.468%	$177.5673	$177.57	$177.55	$177.60
Purchase #5	$145.49	4.519%	$152.0647	$152.06	$152.05	$152.10
Purchase #6	$134.79	5.515%	$142.2237	$142.22	$142.20	$142.20
Purchase #7	$211.57	4.842%	$221.8142	$221.81	$221.80	$221.80
7 purchase totals =	$1,035.76		$1,112.9026	$1,112.90	$1,112.85	$1,113.00