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	$172.86	4.313%	$180.3155	$180.32	$180.30	$180.30
Purchase #2	$45.67	6.136%	$48.4723	$48.47	$48.45	$48.50
Purchase #3	$60.71	4.348%	$63.3497	$63.35	$63.35	$63.30
Purchase #4	$53.42	6.741%	$57.021	$57.02	$57.00	$57.00
Purchase #5	$101.66	11.106%	$112.9504	$112.95	$112.95	$113.00
Purchase #6	$174.39	7.382%	$187.2635	$187.26	$187.25	$187.30
Purchase #7	$85.94	4.544%	$89.8451	$89.85	$89.85	$89.80
7 purchase totals =	$694.65		$739.2175	$739.22	$739.15	$739.20