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	$176.69	11.260%	$196.5853	$196.59	$196.60	$196.60
Purchase #2	$136.90	10.224%	$150.8967	$150.90	$150.90	$150.90
Purchase #3	$102.43	7.535%	$110.1481	$110.15	$110.15	$110.10
Purchase #4	$184.60	3.317%	$190.7232	$190.72	$190.70	$190.70
Purchase #5	$68.87	10.290%	$75.9567	$75.96	$75.95	$76.00
Purchase #6	$56.39	11.543%	$62.8991	$62.90	$62.90	$62.90
Purchase #7	$75.72	10.670%	$83.7993	$83.80	$83.80	$83.80
7 purchase totals =	$801.60		$871.0084	$871.02	$871.00	$871.00