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	$48.86	11.400%	$54.43	$54.43	$54.45	$54.40
Purchase #2	$127.65	10.716%	$141.329	$141.33	$141.35	$141.30
Purchase #3	$139.31	3.721%	$144.4937	$144.49	$144.50	$144.50
Purchase #4	$124.39	9.583%	$136.3103	$136.31	$136.30	$136.30
Purchase #5	$197.70	11.796%	$221.0207	$221.02	$221.00	$221.00
Purchase #6	$172.53	11.676%	$192.6746	$192.67	$192.65	$192.70
Purchase #7	$106.83	9.346%	$116.8143	$116.81	$116.80	$116.80
7 purchase totals =	$917.27		$1,007.0726	$1,007.06	$1,007.05	$1,007.00