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	$158.42	7.397%	$170.1383	$170.14	$170.15	$170.10
Purchase #2	$172.26	10.303%	$190.0079	$190.01	$190.00	$190.00
Purchase #3	$6.89	5.310%	$7.2559	$7.26	$7.25	$7.30
Purchase #4	$73.86	4.256%	$77.0035	$77.00	$77.00	$77.00
Purchase #5	$240.62	7.855%	$259.5207	$259.52	$259.50	$259.50
Purchase #6	$40.69	6.181%	$43.205	$43.21	$43.20	$43.20
Purchase #7	$47.72	9.443%	$52.2262	$52.23	$52.25	$52.20
7 purchase totals =	$740.46		$799.3575	$799.37	$799.35	$799.30