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	$11.37	4.490%	$11.8805	$11.88	$11.90	$11.90
Purchase #2	$241.63	13.183%	$273.4841	$273.48	$273.50	$273.50
Purchase #3	$97.42	3.581%	$100.9086	$100.91	$100.90	$100.90
Purchase #4	$214.55	12.381%	$241.1134	$241.11	$241.10	$241.10
Purchase #5	$194.29	11.709%	$217.0394	$217.04	$217.05	$217.00
Purchase #6	$185.91	5.196%	$195.5699	$195.57	$195.55	$195.60
Purchase #7	$174.54	12.360%	$196.1131	$196.11	$196.10	$196.10
7 purchase totals =	$1,119.71		$1,236.1090	$1,236.10	$1,236.10	$1,236.10