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	$40.88	12.146%	$45.8453	$45.85	$45.85	$45.80
Purchase #2	$93.92	4.490%	$98.137	$98.14	$98.15	$98.10
Purchase #3	$180.90	10.793%	$200.4245	$200.42	$200.40	$200.40
Purchase #4	$10.36	8.479%	$11.2384	$11.24	$11.25	$11.20
Purchase #5	$136.81	7.663%	$147.2938	$147.29	$147.30	$147.30
Purchase #6	$50.90	13.660%	$57.8529	$57.85	$57.85	$57.90
Purchase #7	$166.67	12.373%	$187.2921	$187.29	$187.30	$187.30
7 purchase totals =	$680.44		$748.0840	$748.08	$748.10	$748.00