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	$192.91	13.611%	$219.167	$219.17	$219.15	$219.20
Purchase #2	$150.53	3.826%	$156.2893	$156.29	$156.30	$156.30
Purchase #3	$89.26	7.244%	$95.726	$95.73	$95.75	$95.70
Purchase #4	$247.35	3.554%	$256.1408	$256.14	$256.15	$256.10
Purchase #5	$209.46	10.523%	$231.5015	$231.50	$231.50	$231.50
Purchase #6	$55.31	5.777%	$58.5053	$58.51	$58.50	$58.50
Purchase #7	$244.39	10.436%	$269.8945	$269.89	$269.90	$269.90
7 purchase totals =	$1,189.21		$1,287.2244	$1,287.23	$1,287.25	$1,287.20