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	$64.80	12.539%	$72.9253	$72.93	$72.95	$72.90
Purchase #2	$215.66	4.430%	$225.2137	$225.21	$225.20	$225.20
Purchase #3	$54.56	5.555%	$57.5908	$57.59	$57.60	$57.60
Purchase #4	$127.52	10.567%	$140.995	$141.00	$141.00	$141.00
Purchase #5	$187.30	4.837%	$196.3597	$196.36	$196.35	$196.40
Purchase #6	$136.72	8.677%	$148.5832	$148.58	$148.60	$148.60
Purchase #7	$54.58	9.743%	$59.8977	$59.90	$59.90	$59.90
7 purchase totals =	$841.14		$901.5654	$901.57	$901.60	$901.60