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	$163.47	3.520%	$169.2241	$169.22	$169.20	$169.20
Purchase #2	$65.93	6.605%	$70.2847	$70.28	$70.30	$70.30
Purchase #3	$147.88	13.309%	$167.5613	$167.56	$167.55	$167.60
Purchase #4	$177.76	10.546%	$196.5066	$196.51	$196.50	$196.50
Purchase #5	$20.34	5.830%	$21.5258	$21.53	$21.55	$21.50
Purchase #6	$178.99	3.549%	$185.3424	$185.34	$185.35	$185.30
Purchase #7	$128.70	9.396%	$140.7927	$140.79	$140.80	$140.80
7 purchase totals =	$883.07		$951.2376	$951.23	$951.25	$951.20