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	$69.94	9.836%	$76.8193	$76.82	$76.80	$76.80
Purchase #2	$76.71	8.429%	$83.1759	$83.18	$83.20	$83.20
Purchase #3	$20.68	5.818%	$21.8832	$21.88	$21.90	$21.90
Purchase #4	$146.93	3.489%	$152.0564	$152.06	$152.05	$152.10
Purchase #5	$160.92	11.694%	$179.738	$179.74	$179.75	$179.70
Purchase #6	$132.67	3.751%	$137.6465	$137.65	$137.65	$137.60
Purchase #7	$178.78	3.415%	$184.8853	$184.89	$184.90	$184.90
7 purchase totals =	$786.63		$836.2046	$836.22	$836.25	$836.20