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	$235.53	5.178%	$247.7257	$247.73	$247.75	$247.70
Purchase #2	$219.51	7.691%	$236.3925	$236.39	$236.40	$236.40
Purchase #3	$66.50	6.790%	$71.0154	$71.02	$71.00	$71.00
Purchase #4	$203.47	13.688%	$231.321	$231.32	$231.30	$231.30
Purchase #5	$13.79	10.446%	$15.2305	$15.23	$15.25	$15.20
Purchase #6	$108.99	3.473%	$112.7752	$112.78	$112.80	$112.80
Purchase #7	$139.43	5.275%	$146.7849	$146.78	$146.80	$146.80
7 purchase totals =	$987.22		$1,061.2452	$1,061.25	$1,061.30	$1,061.20