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	$103.66	8.212%	$112.1726	$112.17	$112.15	$112.20
Purchase #2	$248.78	10.519%	$274.9492	$274.95	$274.95	$274.90
Purchase #3	$80.78	11.263%	$89.8783	$89.88	$89.90	$89.90
Purchase #4	$101.61	9.493%	$111.2558	$111.26	$111.25	$111.30
Purchase #5	$232.67	11.258%	$258.864	$258.86	$258.85	$258.90
Purchase #6	$125.33	8.756%	$136.3039	$136.30	$136.30	$136.30
Purchase #7	$153.95	4.692%	$161.1733	$161.17	$161.15	$161.20
7 purchase totals =	$1,046.78		$1,144.5971	$1,144.59	$1,144.55	$1,144.70