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	$99.86	4.527%	$104.3807	$104.38	$104.40	$104.40
Purchase #2	$201.51	13.679%	$229.0746	$229.07	$229.05	$229.10
Purchase #3	$229.48	13.475%	$260.4024	$260.40	$260.40	$260.40
Purchase #4	$48.94	6.856%	$52.2953	$52.30	$52.30	$52.30
Purchase #5	$36.69	10.255%	$40.4526	$40.45	$40.45	$40.50
Purchase #6	$186.86	11.855%	$209.0123	$209.01	$209.00	$209.00
Purchase #7	$62.99	3.822%	$65.3975	$65.40	$65.40	$65.40
7 purchase totals =	$866.33		$961.0154	$961.01	$961.00	$961.10