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	$43.71	4.416%	$45.6402	$45.64	$45.65	$45.60
Purchase #2	$11.51	10.312%	$12.6969	$12.70	$12.70	$12.70
Purchase #3	$28.30	12.681%	$31.8887	$31.89	$31.90	$31.90
Purchase #4	$154.31	13.680%	$175.4196	$175.42	$175.40	$175.40
Purchase #5	$161.92	4.388%	$169.025	$169.03	$169.05	$169.00
Purchase #6	$216.29	4.406%	$225.8197	$225.82	$225.80	$225.80
Purchase #7	$74.85	5.267%	$78.7923	$78.79	$78.80	$78.80
7 purchase totals =	$690.89		$739.2824	$739.29	$739.30	$739.20