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	$112.40	6.298%	$119.479	$119.48	$119.50	$119.50
Purchase #2	$45.28	12.502%	$50.9409	$50.94	$50.95	$50.90
Purchase #3	$246.93	9.298%	$269.8896	$269.89	$269.90	$269.90
Purchase #4	$239.91	13.443%	$272.1611	$272.16	$272.15	$272.20
Purchase #5	$77.87	11.366%	$86.7207	$86.72	$86.70	$86.70
Purchase #6	$190.25	9.532%	$208.3846	$208.38	$208.40	$208.40
Purchase #7	$126.91	5.413%	$133.7796	$133.78	$133.80	$133.80
7 purchase totals =	$1,039.55		$1,141.3555	$1,141.35	$1,141.40	$1,141.40