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	$32.51	7.253%	$34.868	$34.87	$34.85	$34.90
Purchase #2	$46.28	5.274%	$48.7208	$48.72	$48.70	$48.70
Purchase #3	$149.60	5.874%	$158.3875	$158.39	$158.40	$158.40
Purchase #4	$68.39	5.229%	$71.9661	$71.97	$71.95	$72.00
Purchase #5	$231.76	8.284%	$250.959	$250.96	$250.95	$251.00
Purchase #6	$247.98	10.334%	$273.6063	$273.61	$273.60	$273.60
Purchase #7	$136.54	5.365%	$143.8654	$143.87	$143.85	$143.90
7 purchase totals =	$913.06		$982.3731	$982.39	$982.30	$982.50