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	$145.72	4.865%	$152.8093	$152.81	$152.80	$152.80
Purchase #2	$198.29	11.376%	$220.8475	$220.85	$220.85	$220.80
Purchase #3	$31.45	9.786%	$34.5277	$34.53	$34.55	$34.50
Purchase #4	$122.97	13.321%	$139.3508	$139.35	$139.35	$139.40
Purchase #5	$165.55	4.181%	$172.4716	$172.47	$172.45	$172.50
Purchase #6	$130.54	10.504%	$144.2519	$144.25	$144.25	$144.30
Purchase #7	$250.62	10.534%	$277.0203	$277.02	$277.00	$277.00
7 purchase totals =	$1,045.14		$1,141.2791	$1,141.28	$1,141.25	$1,141.30