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	$116.42	13.790%	$132.4743	$132.47	$132.45	$132.50
Purchase #2	$87.84	5.353%	$92.5421	$92.54	$92.55	$92.50
Purchase #3	$201.94	13.776%	$229.7593	$229.76	$229.75	$229.80
Purchase #4	$129.40	3.460%	$133.8772	$133.88	$133.90	$133.90
Purchase #5	$199.26	11.526%	$222.2267	$222.23	$222.25	$222.20
Purchase #6	$156.78	13.354%	$177.7164	$177.72	$177.70	$177.70
Purchase #7	$41.75	9.778%	$45.8323	$45.83	$45.85	$45.80
7 purchase totals =	$933.39		$1,034.4283	$1,034.43	$1,034.45	$1,034.40