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	$246.54	3.184%	$254.3898	$254.39	$254.40	$254.40
Purchase #2	$216.34	7.318%	$232.1718	$232.17	$232.15	$232.20
Purchase #3	$151.47	5.493%	$159.7902	$159.79	$159.80	$159.80
Purchase #4	$82.45	10.195%	$90.8558	$90.86	$90.85	$90.90
Purchase #5	$203.93	11.781%	$227.955	$227.96	$227.95	$228.00
Purchase #6	$88.52	11.685%	$98.8636	$98.86	$98.85	$98.90
Purchase #7	$20.70	3.506%	$21.4257	$21.43	$21.45	$21.40
7 purchase totals =	$1,009.95		$1,085.4519	$1,085.46	$1,085.45	$1,085.60