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	$150.51	7.375%	$161.6101	$161.61	$161.60	$161.60
Purchase #2	$227.38	12.530%	$255.8707	$255.87	$255.85	$255.90
Purchase #3	$222.53	6.162%	$236.2423	$236.24	$236.25	$236.20
Purchase #4	$236.54	10.401%	$261.1425	$261.14	$261.15	$261.10
Purchase #5	$41.56	8.505%	$45.0947	$45.09	$45.10	$45.10
Purchase #6	$113.40	8.482%	$123.0186	$123.02	$123.00	$123.00
Purchase #7	$57.85	3.469%	$59.8568	$59.86	$59.85	$59.90
7 purchase totals =	$1,049.77		$1,142.8357	$1,142.83	$1,142.80	$1,142.80