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	$11.38	4.517%	$11.894	$11.89	$11.90	$11.90
Purchase #2	$67.37	10.330%	$74.3293	$74.33	$74.35	$74.30
Purchase #3	$131.34	12.563%	$147.8402	$147.84	$147.85	$147.80
Purchase #4	$69.84	3.779%	$72.4793	$72.48	$72.50	$72.50
Purchase #5	$40.82	7.263%	$43.7848	$43.78	$43.80	$43.80
Purchase #6	$27.93	13.169%	$31.6081	$31.61	$31.60	$31.60
Purchase #7	$214.39	10.763%	$237.4648	$237.46	$237.45	$237.50
7 purchase totals =	$563.07		$619.4005	$619.39	$619.45	$619.40