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	$126.90	13.401%	$143.9059	$143.91	$143.90	$143.90
Purchase #2	$77.75	7.229%	$83.3705	$83.37	$83.35	$83.40
Purchase #3	$12.37	6.326%	$13.1525	$13.15	$13.15	$13.20
Purchase #4	$232.39	4.178%	$242.0993	$242.10	$242.10	$242.10
Purchase #5	$111.95	12.662%	$126.1251	$126.13	$126.15	$126.10
Purchase #6	$125.37	4.550%	$131.0743	$131.07	$131.05	$131.10
Purchase #7	$18.51	13.439%	$20.9976	$21.00	$21.00	$21.00
7 purchase totals =	$705.24		$760.7252	$760.73	$760.70	$760.80