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	$158.26	5.275%	$166.6082	$166.61	$166.60	$166.60
Purchase #2	$212.87	4.439%	$222.3193	$222.32	$222.30	$222.30
Purchase #3	$244.66	8.700%	$265.9454	$265.95	$265.95	$265.90
Purchase #4	$78.74	5.182%	$82.8203	$82.82	$82.80	$82.80
Purchase #5	$225.39	8.660%	$244.9088	$244.91	$244.90	$244.90
Purchase #6	$176.66	13.545%	$200.5886	$200.59	$200.60	$200.60
Purchase #7	$205.48	8.285%	$222.504	$222.50	$222.50	$222.50
7 purchase totals =	$1,302.06		$1,405.6946	$1,405.70	$1,405.65	$1,405.60