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	$184.50	8.438%	$200.0681	$200.07	$200.05	$200.10
Purchase #2	$249.30	10.507%	$275.494	$275.49	$275.50	$275.50
Purchase #3	$244.96	3.198%	$252.7938	$252.79	$252.80	$252.80
Purchase #4	$201.74	10.344%	$222.608	$222.61	$222.60	$222.60
Purchase #5	$47.37	13.528%	$53.7782	$53.78	$53.80	$53.80
Purchase #6	$116.90	12.338%	$131.3231	$131.32	$131.30	$131.30
Purchase #7	$56.42	12.131%	$63.2643	$63.26	$63.25	$63.30
7 purchase totals =	$1,101.19		$1,199.3295	$1,199.32	$1,199.30	$1,199.40