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	$241.52	6.183%	$256.4532	$256.45	$256.45	$256.50
Purchase #2	$70.55	4.149%	$73.4771	$73.48	$73.50	$73.50
Purchase #3	$108.92	13.111%	$123.2005	$123.20	$123.20	$123.20
Purchase #4	$79.76	10.529%	$88.1579	$88.16	$88.15	$88.20
Purchase #5	$247.62	6.698%	$264.2056	$264.21	$264.20	$264.20
Purchase #6	$52.67	3.367%	$54.4434	$54.44	$54.45	$54.40
Purchase #7	$140.59	6.701%	$150.0109	$150.01	$150.00	$150.00
7 purchase totals =	$941.63		$1,009.9486	$1,009.95	$1,009.95	$1,010.00