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	$11.37	11.418%	$12.6682	$12.67	$12.65	$12.70
Purchase #2	$87.53	6.291%	$93.0365	$93.04	$93.05	$93.00
Purchase #3	$100.80	10.753%	$111.639	$111.64	$111.65	$111.60
Purchase #4	$163.61	11.343%	$182.1683	$182.17	$182.15	$182.20
Purchase #5	$92.85	12.121%	$104.1043	$104.10	$104.10	$104.10
Purchase #6	$91.82	7.210%	$98.4402	$98.44	$98.45	$98.40
Purchase #7	$110.50	11.592%	$123.3092	$123.31	$123.30	$123.30
7 purchase totals =	$658.48		$725.3657	$725.37	$725.35	$725.30