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	$202.98	13.401%	$230.1813	$230.18	$230.20	$230.20
Purchase #2	$146.72	7.653%	$157.9485	$157.95	$157.95	$157.90
Purchase #3	$43.72	3.199%	$45.1186	$45.12	$45.10	$45.10
Purchase #4	$160.31	5.292%	$168.7936	$168.79	$168.80	$168.80
Purchase #5	$138.40	3.747%	$143.5858	$143.59	$143.60	$143.60
Purchase #6	$51.88	9.545%	$56.8319	$56.83	$56.85	$56.80
Purchase #7	$57.33	6.468%	$61.0381	$61.04	$61.05	$61.00
7 purchase totals =	$801.34		$863.4978	$863.50	$863.55	$863.40