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	$147.77	6.283%	$157.0544	$157.05	$157.05	$157.10
Purchase #2	$37.77	7.340%	$40.5423	$40.54	$40.55	$40.50
Purchase #3	$162.70	11.207%	$180.9338	$180.93	$180.95	$180.90
Purchase #4	$130.67	12.102%	$146.4837	$146.48	$146.50	$146.50
Purchase #5	$78.61	3.674%	$81.4981	$81.50	$81.50	$81.50
Purchase #6	$226.60	10.240%	$249.8038	$249.80	$249.80	$249.80
Purchase #7	$154.53	9.333%	$168.9523	$168.95	$168.95	$169.00
7 purchase totals =	$938.65		$1,025.2684	$1,025.25	$1,025.30	$1,025.30