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	$13.27	13.600%	$15.0747	$15.07	$15.05	$15.10
Purchase #2	$6.51	10.726%	$7.2083	$7.21	$7.20	$7.20
Purchase #3	$83.31	3.809%	$86.4833	$86.48	$86.50	$86.50
Purchase #4	$237.54	10.281%	$261.9615	$261.96	$261.95	$262.00
Purchase #5	$69.66	4.663%	$72.9082	$72.91	$72.90	$72.90
Purchase #6	$105.63	6.371%	$112.3597	$112.36	$112.35	$112.40
Purchase #7	$186.53	10.340%	$205.8172	$205.82	$205.80	$205.80
7 purchase totals =	$702.45		$761.8129	$761.81	$761.75	$761.90