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	$91.57	12.698%	$103.1976	$103.20	$103.20	$103.20
Purchase #2	$157.41	11.502%	$175.5153	$175.52	$175.50	$175.50
Purchase #3	$87.89	5.344%	$92.5868	$92.59	$92.60	$92.60
Purchase #4	$178.99	11.404%	$199.402	$199.40	$199.40	$199.40
Purchase #5	$148.99	12.198%	$167.1638	$167.16	$167.15	$167.20
Purchase #6	$105.48	5.211%	$110.9766	$110.98	$111.00	$111.00
Purchase #7	$151.40	11.659%	$169.0517	$169.05	$169.05	$169.10
7 purchase totals =	$921.73		$1,017.8938	$1,017.90	$1,017.90	$1,018.00