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	$178.25	7.653%	$191.8915	$191.89	$191.90	$191.90
Purchase #2	$57.51	13.858%	$65.4797	$65.48	$65.50	$65.50
Purchase #3	$37.96	7.832%	$40.933	$40.93	$40.95	$40.90
Purchase #4	$118.62	7.459%	$127.4679	$127.47	$127.45	$127.50
Purchase #5	$51.34	12.539%	$57.7775	$57.78	$57.80	$57.80
Purchase #6	$218.64	11.160%	$243.0402	$243.04	$243.05	$243.00
Purchase #7	$150.60	8.786%	$163.8317	$163.83	$163.85	$163.80
7 purchase totals =	$812.92		$890.4215	$890.42	$890.50	$890.40