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	$237.88	4.599%	$248.8201	$248.82	$248.80	$248.80
Purchase #2	$189.88	8.259%	$205.5622	$205.56	$205.55	$205.60
Purchase #3	$35.75	10.511%	$39.5077	$39.51	$39.50	$39.50
Purchase #4	$233.66	11.233%	$259.907	$259.91	$259.90	$259.90
Purchase #5	$39.87	8.580%	$43.2908	$43.29	$43.30	$43.30
Purchase #6	$172.65	10.551%	$190.8663	$190.87	$190.85	$190.90
Purchase #7	$145.72	6.505%	$155.1991	$155.20	$155.20	$155.20
7 purchase totals =	$1,055.41		$1,143.1532	$1,143.16	$1,143.10	$1,143.20