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	$146.56	3.810%	$152.1439	$152.14	$152.15	$152.10
Purchase #2	$191.66	13.859%	$218.2222	$218.22	$218.20	$218.20
Purchase #3	$83.79	4.508%	$87.5673	$87.57	$87.55	$87.60
Purchase #4	$168.60	13.795%	$191.8584	$191.86	$191.85	$191.90
Purchase #5	$11.55	9.592%	$12.6579	$12.66	$12.65	$12.70
Purchase #6	$115.87	6.340%	$123.2162	$123.22	$123.20	$123.20
Purchase #7	$208.94	3.554%	$216.3657	$216.37	$216.35	$216.40
7 purchase totals =	$926.97		$1,002.0316	$1,002.04	$1,001.95	$1,002.10