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	$197.76	13.856%	$225.1616	$225.16	$225.15	$225.20
Purchase #2	$76.28	10.486%	$84.2787	$84.28	$84.30	$84.30
Purchase #3	$91.44	11.482%	$101.9391	$101.94	$101.95	$101.90
Purchase #4	$87.78	4.728%	$91.9302	$91.93	$91.95	$91.90
Purchase #5	$100.93	10.755%	$111.785	$111.79	$111.80	$111.80
Purchase #6	$63.42	13.766%	$72.1504	$72.15	$72.15	$72.20
Purchase #7	$186.33	13.722%	$211.8982	$211.90	$211.90	$211.90
7 purchase totals =	$803.94		$899.1432	$899.15	$899.20	$899.20