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	$143.62	4.156%	$149.5888	$149.59	$149.60	$149.60
Purchase #2	$40.90	13.452%	$46.4019	$46.40	$46.40	$46.40
Purchase #3	$142.41	5.252%	$149.8894	$149.89	$149.90	$149.90
Purchase #4	$176.51	13.805%	$200.8772	$200.88	$200.90	$200.90
Purchase #5	$58.91	10.215%	$64.9277	$64.93	$64.95	$64.90
Purchase #6	$30.49	8.741%	$33.1551	$33.16	$33.15	$33.20
Purchase #7	$110.80	5.225%	$116.5893	$116.59	$116.60	$116.60
7 purchase totals =	$703.64		$761.4294	$761.44	$761.50	$761.50