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	$225.66	4.645%	$236.1419	$236.14	$236.15	$236.10
Purchase #2	$239.98	13.106%	$271.4318	$271.43	$271.45	$271.40
Purchase #3	$95.37	5.130%	$100.2625	$100.26	$100.25	$100.30
Purchase #4	$148.86	13.281%	$168.6301	$168.63	$168.65	$168.60
Purchase #5	$197.95	10.432%	$218.6001	$218.60	$218.60	$218.60
Purchase #6	$199.77	12.447%	$224.6354	$224.64	$224.65	$224.60
Purchase #7	$64.57	12.297%	$72.5102	$72.51	$72.50	$72.50
7 purchase totals =	$1,172.16		$1,292.2120	$1,292.21	$1,292.25	$1,292.10