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	$9.85	11.708%	$11.0032	$11.00	$11.00	$11.00
Purchase #2	$42.30	6.650%	$45.113	$45.11	$45.10	$45.10
Purchase #3	$18.45	13.111%	$20.869	$20.87	$20.85	$20.90
Purchase #4	$47.84	9.335%	$52.3059	$52.31	$52.30	$52.30
Purchase #5	$29.92	4.377%	$31.2296	$31.23	$31.25	$31.20
Purchase #6	$27.84	13.817%	$31.6867	$31.69	$31.70	$31.70
Purchase #7	$248.51	12.626%	$279.8869	$279.89	$279.90	$279.90
7 purchase totals =	$424.71		$472.0943	$472.10	$472.10	$472.10