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	$172.72	11.751%	$193.0163	$193.02	$193.00	$193.00
Purchase #2	$94.39	11.415%	$105.1646	$105.16	$105.15	$105.20
Purchase #3	$142.81	6.773%	$152.4825	$152.48	$152.50	$152.50
Purchase #4	$133.44	3.520%	$138.1371	$138.14	$138.15	$138.10
Purchase #5	$42.88	13.347%	$48.6032	$48.60	$48.60	$48.60
Purchase #6	$101.42	9.706%	$111.2638	$111.26	$111.25	$111.30
Purchase #7	$204.49	6.718%	$218.2276	$218.23	$218.25	$218.20
7 purchase totals =	$892.15		$966.8951	$966.89	$966.90	$966.90