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	$24.26	9.109%	$26.4698	$26.47	$26.45	$26.50
Purchase #2	$29.49	13.513%	$33.475	$33.48	$33.50	$33.50
Purchase #3	$243.50	4.556%	$254.5939	$254.59	$254.60	$254.60
Purchase #4	$171.31	9.516%	$187.6119	$187.61	$187.60	$187.60
Purchase #5	$197.72	12.597%	$222.6268	$222.63	$222.65	$222.60
Purchase #6	$12.30	3.241%	$12.6986	$12.70	$12.70	$12.70
Purchase #7	$242.33	9.214%	$264.6583	$264.66	$264.65	$264.70
7 purchase totals =	$920.91		$1,002.1343	$1,002.14	$1,002.15	$1,002.20