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	$221.56	4.139%	$230.7304	$230.73	$230.75	$230.70
Purchase #2	$60.88	8.224%	$65.8868	$65.89	$65.90	$65.90
Purchase #3	$81.54	11.384%	$90.8225	$90.82	$90.80	$90.80
Purchase #4	$30.58	12.180%	$34.3046	$34.30	$34.30	$34.30
Purchase #5	$148.35	10.446%	$163.8466	$163.85	$163.85	$163.80
Purchase #6	$240.76	6.286%	$255.8942	$255.89	$255.90	$255.90
Purchase #7	$207.55	8.759%	$225.7293	$225.73	$225.75	$225.70
7 purchase totals =	$991.22		$1,067.2144	$1,067.21	$1,067.25	$1,067.10