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	$134.47	13.257%	$152.2967	$152.30	$152.30	$152.30
Purchase #2	$148.93	5.426%	$157.0109	$157.01	$157.00	$157.00
Purchase #3	$61.73	8.426%	$66.9314	$66.93	$66.95	$66.90
Purchase #4	$65.54	10.667%	$72.5312	$72.53	$72.55	$72.50
Purchase #5	$165.79	11.850%	$185.4361	$185.44	$185.45	$185.40
Purchase #6	$242.51	12.340%	$272.4357	$272.44	$272.45	$272.40
Purchase #7	$164.76	5.131%	$173.2138	$173.21	$173.20	$173.20
7 purchase totals =	$983.73		$1,079.8558	$1,079.86	$1,079.90	$1,079.70