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	$122.47	7.691%	$131.8892	$131.89	$131.90	$131.90
Purchase #2	$157.35	9.815%	$172.7939	$172.79	$172.80	$172.80
Purchase #3	$242.49	10.617%	$268.2352	$268.24	$268.25	$268.20
Purchase #4	$155.54	13.248%	$176.1459	$176.15	$176.15	$176.10
Purchase #5	$216.74	7.286%	$232.5317	$232.53	$232.55	$232.50
Purchase #6	$175.94	11.673%	$196.4775	$196.48	$196.50	$196.50
Purchase #7	$78.51	10.347%	$86.6334	$86.63	$86.65	$86.60
7 purchase totals =	$1,149.04		$1,264.7068	$1,264.71	$1,264.80	$1,264.60