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	$76.79	13.626%	$87.2534	$87.25	$87.25	$87.30
Purchase #2	$48.32	12.804%	$54.5069	$54.51	$54.50	$54.50
Purchase #3	$122.71	3.701%	$127.2515	$127.25	$127.25	$127.30
Purchase #4	$18.60	10.190%	$20.4953	$20.50	$20.50	$20.50
Purchase #5	$109.96	5.581%	$116.0969	$116.10	$116.10	$116.10
Purchase #6	$60.94	4.762%	$63.842	$63.84	$63.85	$63.80
Purchase #7	$28.54	12.750%	$32.1789	$32.18	$32.20	$32.20
7 purchase totals =	$465.86		$501.6249	$501.63	$501.65	$501.70