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	$232.55	3.490%	$240.666	$240.67	$240.65	$240.70
Purchase #2	$32.69	13.315%	$37.0427	$37.04	$37.05	$37.00
Purchase #3	$19.63	5.850%	$20.7784	$20.78	$20.80	$20.80
Purchase #4	$140.31	12.687%	$158.1111	$158.11	$158.10	$158.10
Purchase #5	$148.45	6.561%	$158.1898	$158.19	$158.20	$158.20
Purchase #6	$108.34	10.179%	$119.3679	$119.37	$119.35	$119.40
Purchase #7	$250.36	4.828%	$262.4474	$262.45	$262.45	$262.40
7 purchase totals =	$932.33		$996.6033	$996.61	$996.60	$996.60