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	$99.78	12.199%	$111.9522	$111.95	$111.95	$112.00
Purchase #2	$124.59	6.573%	$132.7793	$132.78	$132.80	$132.80
Purchase #3	$88.61	3.482%	$91.6954	$91.70	$91.70	$91.70
Purchase #4	$77.56	7.678%	$83.5151	$83.52	$83.50	$83.50
Purchase #5	$36.26	3.761%	$37.6237	$37.62	$37.60	$37.60
Purchase #6	$222.65	3.213%	$229.8037	$229.80	$229.80	$229.80
Purchase #7	$200.68	13.432%	$227.6353	$227.64	$227.65	$227.60
7 purchase totals =	$850.13		$915.0047	$915.01	$915.00	$915.00