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	$95.66	8.145%	$103.4515	$103.45	$103.45	$103.50
Purchase #2	$197.83	11.249%	$220.0839	$220.08	$220.10	$220.10
Purchase #3	$60.46	12.166%	$67.8156	$67.82	$67.80	$67.80
Purchase #4	$178.91	4.661%	$187.249	$187.25	$187.25	$187.20
Purchase #5	$91.67	12.463%	$103.0948	$103.09	$103.10	$103.10
Purchase #6	$152.90	6.234%	$162.4318	$162.43	$162.45	$162.40
Purchase #7	$42.81	13.326%	$48.5149	$48.51	$48.50	$48.50
7 purchase totals =	$820.24		$892.6415	$892.63	$892.65	$892.60