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	$119.28	4.734%	$124.9267	$124.93	$124.95	$124.90
Purchase #2	$83.38	13.275%	$94.4487	$94.45	$94.45	$94.40
Purchase #3	$150.67	13.753%	$171.3916	$171.39	$171.40	$171.40
Purchase #4	$108.55	8.564%	$117.8462	$117.85	$117.85	$117.80
Purchase #5	$32.72	5.701%	$34.5854	$34.59	$34.60	$34.60
Purchase #6	$9.63	13.437%	$10.924	$10.92	$10.90	$10.90
Purchase #7	$30.75	10.221%	$33.893	$33.89	$33.90	$33.90
7 purchase totals =	$534.98		$588.0156	$588.02	$588.05	$587.90