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	$105.51	13.295%	$119.5376	$119.54	$119.55	$119.50
Purchase #2	$212.85	4.503%	$222.4346	$222.43	$222.45	$222.40
Purchase #3	$213.82	12.389%	$240.3102	$240.31	$240.30	$240.30
Purchase #4	$60.48	4.548%	$63.2306	$63.23	$63.25	$63.20
Purchase #5	$179.55	6.351%	$190.9532	$190.95	$190.95	$191.00
Purchase #6	$26.26	12.623%	$29.5748	$29.57	$29.55	$29.60
Purchase #7	$240.35	13.778%	$273.4654	$273.47	$273.45	$273.50
7 purchase totals =	$1,038.82		$1,139.5064	$1,139.50	$1,139.50	$1,139.50