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	$161.79	5.677%	$170.9748	$170.97	$170.95	$171.00
Purchase #2	$57.52	6.754%	$61.4049	$61.40	$61.40	$61.40
Purchase #3	$140.89	8.484%	$152.8431	$152.84	$152.85	$152.80
Purchase #4	$19.83	3.505%	$20.525	$20.53	$20.55	$20.50
Purchase #5	$246.49	13.523%	$279.8228	$279.82	$279.80	$279.80
Purchase #6	$130.33	8.378%	$141.249	$141.25	$141.25	$141.20
Purchase #7	$192.88	11.478%	$215.0188	$215.02	$215.00	$215.00
7 purchase totals =	$949.73		$1,041.8384	$1,041.83	$1,041.80	$1,041.70