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	$245.52	7.677%	$264.3686	$264.37	$264.35	$264.40
Purchase #2	$172.75	12.250%	$193.9119	$193.91	$193.90	$193.90
Purchase #3	$104.78	8.745%	$113.943	$113.94	$113.95	$113.90
Purchase #4	$163.45	4.730%	$171.1812	$171.18	$171.20	$171.20
Purchase #5	$43.61	3.439%	$45.1097	$45.11	$45.10	$45.10
Purchase #6	$127.46	10.637%	$141.0179	$141.02	$141.00	$141.00
Purchase #7	$139.91	3.528%	$144.846	$144.85	$144.85	$144.80
7 purchase totals =	$997.48		$1,074.3783	$1,074.38	$1,074.35	$1,074.30