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	$77.50	10.689%	$85.784	$85.78	$85.80	$85.80
Purchase #2	$22.86	10.614%	$25.2864	$25.29	$25.30	$25.30
Purchase #3	$119.44	3.428%	$123.5344	$123.53	$123.55	$123.50
Purchase #4	$123.50	3.491%	$127.8114	$127.81	$127.80	$127.80
Purchase #5	$128.41	6.756%	$137.0854	$137.09	$137.10	$137.10
Purchase #6	$112.43	13.849%	$128.0004	$128.00	$128.00	$128.00
Purchase #7	$208.50	4.547%	$217.9805	$217.98	$218.00	$218.00
7 purchase totals =	$792.64		$845.4825	$845.48	$845.55	$845.50