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	$189.59	13.812%	$215.7762	$215.78	$215.80	$215.80
Purchase #2	$151.77	11.234%	$168.8198	$168.82	$168.80	$168.80
Purchase #3	$109.76	11.855%	$122.772	$122.77	$122.75	$122.80
Purchase #4	$151.46	4.534%	$158.3272	$158.33	$158.35	$158.30
Purchase #5	$237.85	8.206%	$257.368	$257.37	$257.35	$257.40
Purchase #6	$27.44	7.865%	$29.5982	$29.60	$29.60	$29.60
Purchase #7	$145.42	3.731%	$150.8456	$150.85	$150.85	$150.80
7 purchase totals =	$1,013.29		$1,103.5070	$1,103.52	$1,103.50	$1,103.50