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	$60.28	11.645%	$67.2996	$67.30	$67.30	$67.30
Purchase #2	$99.62	13.682%	$113.25	$113.25	$113.25	$113.30
Purchase #3	$250.45	6.347%	$266.3461	$266.35	$266.35	$266.30
Purchase #4	$67.94	9.584%	$74.4514	$74.45	$74.45	$74.50
Purchase #5	$237.93	11.589%	$265.5037	$265.50	$265.50	$265.50
Purchase #6	$78.27	9.453%	$85.6689	$85.67	$85.65	$85.70
Purchase #7	$86.63	5.670%	$91.5419	$91.54	$91.55	$91.50
7 purchase totals =	$881.12		$964.0616	$964.06	$964.05	$964.10