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	$81.70	4.860%	$85.6706	$85.67	$85.65	$85.70
Purchase #2	$235.79	13.427%	$267.4495	$267.45	$267.45	$267.40
Purchase #3	$248.95	4.792%	$260.8797	$260.88	$260.90	$260.90
Purchase #4	$69.53	11.472%	$77.5065	$77.51	$77.50	$77.50
Purchase #5	$170.79	8.681%	$185.6163	$185.62	$185.60	$185.60
Purchase #6	$24.40	12.299%	$27.401	$27.40	$27.40	$27.40
Purchase #7	$41.28	3.119%	$42.5675	$42.57	$42.55	$42.60
7 purchase totals =	$872.44		$947.0911	$947.10	$947.05	$947.10