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	$217.98	9.512%	$238.7143	$238.71	$238.70	$238.70
Purchase #2	$165.38	11.708%	$184.7427	$184.74	$184.75	$184.70
Purchase #3	$29.79	5.419%	$31.4043	$31.40	$31.40	$31.40
Purchase #4	$137.95	13.603%	$156.7153	$156.72	$156.70	$156.70
Purchase #5	$139.44	10.351%	$153.8734	$153.87	$153.85	$153.90
Purchase #6	$90.65	10.739%	$100.3849	$100.38	$100.40	$100.40
Purchase #7	$50.70	4.471%	$52.9668	$52.97	$52.95	$53.00
7 purchase totals =	$831.89		$918.8017	$918.79	$918.75	$918.80