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	$58.86	10.266%	$64.9026	$64.90	$64.90	$64.90
Purchase #2	$159.59	8.353%	$172.9206	$172.92	$172.90	$172.90
Purchase #3	$40.68	4.801%	$42.633	$42.63	$42.65	$42.60
Purchase #4	$203.77	9.344%	$222.8103	$222.81	$222.80	$222.80
Purchase #5	$105.90	11.254%	$117.818	$117.82	$117.80	$117.80
Purchase #6	$84.93	3.587%	$87.9764	$87.98	$88.00	$88.00
Purchase #7	$92.75	6.227%	$98.5255	$98.53	$98.55	$98.50
7 purchase totals =	$746.48		$807.5864	$807.59	$807.60	$807.50