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	$78.53	13.802%	$89.3687	$89.37	$89.35	$89.40
Purchase #2	$142.26	11.554%	$158.6967	$158.70	$158.70	$158.70
Purchase #3	$136.74	11.322%	$152.2217	$152.22	$152.20	$152.20
Purchase #4	$215.95	11.845%	$241.5293	$241.53	$241.55	$241.50
Purchase #5	$77.48	6.475%	$82.4968	$82.50	$82.50	$82.50
Purchase #6	$184.56	5.393%	$194.5133	$194.51	$194.50	$194.50
Purchase #7	$112.55	3.224%	$116.1786	$116.18	$116.20	$116.20
7 purchase totals =	$948.07		$1,035.0051	$1,035.01	$1,035.00	$1,035.00