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	$190.91	4.687%	$199.858	$199.86	$199.85	$199.90
Purchase #2	$198.40	8.503%	$215.27	$215.27	$215.25	$215.30
Purchase #3	$79.34	4.566%	$82.9627	$82.96	$82.95	$83.00
Purchase #4	$6.87	8.870%	$7.4794	$7.48	$7.50	$7.50
Purchase #5	$227.37	8.520%	$246.7419	$246.74	$246.75	$246.70
Purchase #6	$70.88	11.298%	$78.888	$78.89	$78.90	$78.90
Purchase #7	$138.84	5.765%	$146.8441	$146.84	$146.85	$146.80
7 purchase totals =	$912.61		$978.0441	$978.04	$978.05	$978.10