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	$233.46	9.685%	$256.0706	$256.07	$256.05	$256.10
Purchase #2	$35.50	10.205%	$39.1228	$39.12	$39.10	$39.10
Purchase #3	$51.25	6.747%	$54.7078	$54.71	$54.70	$54.70
Purchase #4	$174.57	12.284%	$196.0142	$196.01	$196.00	$196.00
Purchase #5	$223.86	8.429%	$242.7292	$242.73	$242.75	$242.70
Purchase #6	$179.62	11.517%	$200.3068	$200.31	$200.30	$200.30
Purchase #7	$239.34	10.367%	$264.1524	$264.15	$264.15	$264.20
7 purchase totals =	$1,137.60		$1,253.1038	$1,253.10	$1,253.05	$1,253.10