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	$232.31	13.369%	$263.3675	$263.37	$263.35	$263.40
Purchase #2	$155.81	3.593%	$161.4083	$161.41	$161.40	$161.40
Purchase #3	$164.78	13.584%	$187.1637	$187.16	$187.15	$187.20
Purchase #4	$209.39	9.158%	$228.5659	$228.57	$228.55	$228.60
Purchase #5	$64.50	11.705%	$72.0497	$72.05	$72.05	$72.00
Purchase #6	$184.32	3.161%	$190.1464	$190.15	$190.15	$190.10
Purchase #7	$158.48	6.321%	$168.4975	$168.50	$168.50	$168.50
7 purchase totals =	$1,169.59		$1,271.1990	$1,271.21	$1,271.15	$1,271.20