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	$98.49	11.102%	$109.4244	$109.42	$109.40	$109.40
Purchase #2	$137.47	11.129%	$152.769	$152.77	$152.75	$152.80
Purchase #3	$34.38	12.868%	$38.804	$38.80	$38.80	$38.80
Purchase #4	$104.43	3.142%	$107.7112	$107.71	$107.70	$107.70
Purchase #5	$135.89	5.517%	$143.3871	$143.39	$143.40	$143.40
Purchase #6	$247.81	10.103%	$272.8462	$272.85	$272.85	$272.80
Purchase #7	$243.58	6.556%	$259.5491	$259.55	$259.55	$259.50
7 purchase totals =	$1,002.05		$1,084.4910	$1,084.49	$1,084.45	$1,084.40