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	$6.96	13.116%	$7.8729	$7.87	$7.85	$7.90
Purchase #2	$95.62	10.828%	$105.9737	$105.97	$105.95	$106.00
Purchase #3	$215.48	4.829%	$225.8855	$225.89	$225.90	$225.90
Purchase #4	$64.95	6.648%	$69.2679	$69.27	$69.25	$69.30
Purchase #5	$164.94	8.799%	$179.4531	$179.45	$179.45	$179.50
Purchase #6	$42.70	7.207%	$45.7774	$45.78	$45.80	$45.80
Purchase #7	$50.77	11.405%	$56.5603	$56.56	$56.55	$56.60
7 purchase totals =	$641.42		$690.7908	$690.79	$690.75	$691.00