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	$168.76	9.776%	$185.258	$185.26	$185.25	$185.30
Purchase #2	$174.72	6.155%	$185.474	$185.47	$185.45	$185.50
Purchase #3	$100.34	6.148%	$106.5089	$106.51	$106.50	$106.50
Purchase #4	$156.52	12.831%	$176.6031	$176.60	$176.60	$176.60
Purchase #5	$107.70	10.380%	$118.8793	$118.88	$118.90	$118.90
Purchase #6	$76.82	10.732%	$85.0643	$85.06	$85.05	$85.10
Purchase #7	$66.67	7.239%	$71.4962	$71.50	$71.50	$71.50
7 purchase totals =	$851.53		$929.2838	$929.28	$929.25	$929.40