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	$97.48	6.783%	$104.0921	$104.09	$104.10	$104.10
Purchase #2	$213.89	4.772%	$224.0968	$224.10	$224.10	$224.10
Purchase #3	$226.32	6.105%	$240.1368	$240.14	$240.15	$240.10
Purchase #4	$25.78	7.521%	$27.7189	$27.72	$27.70	$27.70
Purchase #5	$176.39	11.761%	$197.1352	$197.14	$197.15	$197.10
Purchase #6	$75.71	4.126%	$78.8338	$78.83	$78.85	$78.80
Purchase #7	$39.26	3.539%	$40.6494	$40.65	$40.65	$40.60
7 purchase totals =	$854.83		$912.6630	$912.67	$912.70	$912.50