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	$94.41	9.444%	$103.3261	$103.33	$103.35	$103.30
Purchase #2	$71.69	13.525%	$81.3861	$81.39	$81.40	$81.40
Purchase #3	$139.64	3.672%	$144.7676	$144.77	$144.75	$144.80
Purchase #4	$218.59	8.115%	$236.3286	$236.33	$236.35	$236.30
Purchase #5	$248.77	12.203%	$279.1274	$279.13	$279.15	$279.10
Purchase #6	$243.79	11.482%	$271.782	$271.78	$271.80	$271.80
Purchase #7	$22.48	13.489%	$25.5123	$25.51	$25.50	$25.50
7 purchase totals =	$1,039.37		$1,142.2301	$1,142.24	$1,142.30	$1,142.20