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	$58.55	3.541%	$60.6233	$60.62	$60.60	$60.60
Purchase #2	$180.26	8.778%	$196.0832	$196.08	$196.10	$196.10
Purchase #3	$131.71	13.535%	$149.5369	$149.54	$149.55	$149.50
Purchase #4	$179.42	10.629%	$198.4906	$198.49	$198.50	$198.50
Purchase #5	$184.58	13.192%	$208.9298	$208.93	$208.95	$208.90
Purchase #6	$127.34	9.792%	$139.8091	$139.81	$139.80	$139.80
Purchase #7	$157.67	7.538%	$169.5552	$169.56	$169.55	$169.60
7 purchase totals =	$1,019.53		$1,123.0281	$1,123.03	$1,123.05	$1,123.00