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	$73.70	13.771%	$83.8492	$83.85	$83.85	$83.80
Purchase #2	$165.56	5.184%	$174.1426	$174.14	$174.15	$174.10
Purchase #3	$66.73	7.734%	$71.8909	$71.89	$71.90	$71.90
Purchase #4	$222.53	11.807%	$248.8041	$248.80	$248.80	$248.80
Purchase #5	$153.41	12.704%	$172.8992	$172.90	$172.90	$172.90
Purchase #6	$105.70	10.850%	$117.1685	$117.17	$117.15	$117.20
Purchase #7	$137.29	12.153%	$153.9749	$153.97	$153.95	$154.00
7 purchase totals =	$924.92		$1,022.7294	$1,022.72	$1,022.70	$1,022.70