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	$90.38	9.620%	$99.0746	$99.07	$99.05	$99.10
Purchase #2	$136.80	6.217%	$145.3049	$145.30	$145.30	$145.30
Purchase #3	$143.71	5.786%	$152.0251	$152.03	$152.05	$152.00
Purchase #4	$247.89	10.639%	$274.263	$274.26	$274.25	$274.30
Purchase #5	$59.65	4.817%	$62.5233	$62.52	$62.50	$62.50
Purchase #6	$132.45	9.654%	$145.2367	$145.24	$145.25	$145.20
Purchase #7	$146.82	9.175%	$160.2907	$160.29	$160.30	$160.30
7 purchase totals =	$957.70		$1,038.7183	$1,038.71	$1,038.70	$1,038.70