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	$104.76	4.657%	$109.6387	$109.64	$109.65	$109.60
Purchase #2	$27.85	13.441%	$31.5933	$31.59	$31.60	$31.60
Purchase #3	$111.78	9.301%	$122.1767	$122.18	$122.20	$122.20
Purchase #4	$165.44	5.175%	$174.0015	$174.00	$174.00	$174.00
Purchase #5	$139.75	6.246%	$148.4788	$148.48	$148.50	$148.50
Purchase #6	$156.33	7.827%	$168.5659	$168.57	$168.55	$168.60
Purchase #7	$125.48	10.317%	$138.4258	$138.43	$138.45	$138.40
7 purchase totals =	$831.39		$892.8807	$892.89	$892.95	$892.90