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	$74.98	5.134%	$78.8295	$78.83	$78.85	$78.80
Purchase #2	$33.33	10.693%	$36.894	$36.89	$36.90	$36.90
Purchase #3	$96.48	8.828%	$104.9973	$105.00	$105.00	$105.00
Purchase #4	$213.81	3.565%	$221.4323	$221.43	$221.45	$221.40
Purchase #5	$22.32	11.556%	$24.8993	$24.90	$24.90	$24.90
Purchase #6	$171.59	8.628%	$186.3948	$186.39	$186.40	$186.40
Purchase #7	$66.25	9.246%	$72.3755	$72.38	$72.40	$72.40
7 purchase totals =	$678.76		$725.8227	$725.82	$725.90	$725.80