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	$86.63	6.591%	$92.3398	$92.34	$92.35	$92.30
Purchase #2	$139.53	9.304%	$152.5119	$152.51	$152.50	$152.50
Purchase #3	$152.37	5.184%	$160.2689	$160.27	$160.25	$160.30
Purchase #4	$34.55	11.696%	$38.591	$38.59	$38.60	$38.60
Purchase #5	$148.89	5.494%	$157.07	$157.07	$157.05	$157.10
Purchase #6	$149.77	6.170%	$159.0108	$159.01	$159.00	$159.00
Purchase #7	$189.88	3.708%	$196.9208	$196.92	$196.90	$196.90
7 purchase totals =	$901.62		$956.7132	$956.71	$956.65	$956.70