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	$213.51	11.455%	$237.9676	$237.97	$237.95	$238.00
Purchase #2	$99.79	3.790%	$103.572	$103.57	$103.55	$103.60
Purchase #3	$51.59	6.399%	$54.8912	$54.89	$54.90	$54.90
Purchase #4	$192.91	13.456%	$218.868	$218.87	$218.85	$218.90
Purchase #5	$51.95	11.602%	$57.9772	$57.98	$58.00	$58.00
Purchase #6	$137.78	9.160%	$150.4006	$150.40	$150.40	$150.40
Purchase #7	$167.69	13.138%	$189.7211	$189.72	$189.70	$189.70
7 purchase totals =	$915.22		$1,013.3977	$1,013.40	$1,013.35	$1,013.50