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	$181.63	4.644%	$190.0649	$190.06	$190.05	$190.10
Purchase #2	$189.41	13.742%	$215.4387	$215.44	$215.45	$215.40
Purchase #3	$37.90	10.825%	$42.0027	$42.00	$42.00	$42.00
Purchase #4	$119.87	11.461%	$133.6083	$133.61	$133.60	$133.60
Purchase #5	$159.86	10.657%	$176.8963	$176.90	$176.90	$176.90
Purchase #6	$138.77	12.729%	$156.434	$156.43	$156.45	$156.40
Purchase #7	$62.46	5.859%	$66.1195	$66.12	$66.10	$66.10
7 purchase totals =	$889.90		$980.5644	$980.56	$980.55	$980.50