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	$63.48	6.175%	$67.3999	$67.40	$67.40	$67.40
Purchase #2	$29.41	13.338%	$33.3327	$33.33	$33.35	$33.30
Purchase #3	$183.87	3.163%	$189.6858	$189.69	$189.70	$189.70
Purchase #4	$19.66	11.114%	$21.845	$21.85	$21.85	$21.80
Purchase #5	$78.31	4.804%	$82.072	$82.07	$82.05	$82.10
Purchase #6	$113.97	8.356%	$123.4933	$123.49	$123.50	$123.50
Purchase #7	$224.65	8.826%	$244.4776	$244.48	$244.50	$244.50
7 purchase totals =	$713.35		$762.3063	$762.31	$762.35	$762.30