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	$141.58	7.807%	$152.6332	$152.63	$152.65	$152.60
Purchase #2	$173.76	13.628%	$197.44	$197.44	$197.45	$197.40
Purchase #3	$38.37	11.636%	$42.8347	$42.83	$42.85	$42.80
Purchase #4	$116.83	10.361%	$128.9348	$128.93	$128.95	$128.90
Purchase #5	$96.95	8.868%	$105.5475	$105.55	$105.55	$105.50
Purchase #6	$175.37	9.288%	$191.6584	$191.66	$191.65	$191.70
Purchase #7	$131.90	10.523%	$145.7798	$145.78	$145.80	$145.80
7 purchase totals =	$874.76		$964.8284	$964.82	$964.90	$964.70