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	$130.96	13.662%	$148.8518	$148.85	$148.85	$148.90
Purchase #2	$60.72	4.770%	$63.6163	$63.62	$63.60	$63.60
Purchase #3	$203.32	9.267%	$222.1617	$222.16	$222.15	$222.20
Purchase #4	$87.44	3.200%	$90.2381	$90.24	$90.25	$90.20
Purchase #5	$217.69	12.848%	$245.6588	$245.66	$245.65	$245.70
Purchase #6	$197.39	6.234%	$209.6953	$209.70	$209.70	$209.70
Purchase #7	$43.83	3.700%	$45.4517	$45.45	$45.45	$45.50
7 purchase totals =	$941.35		$1,025.6737	$1,025.68	$1,025.65	$1,025.80