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	$142.25	7.477%	$152.886	$152.89	$152.90	$152.90
Purchase #2	$201.73	12.801%	$227.5535	$227.55	$227.55	$227.60
Purchase #3	$29.82	5.296%	$31.3993	$31.40	$31.40	$31.40
Purchase #4	$29.72	9.377%	$32.5068	$32.51	$32.50	$32.50
Purchase #5	$226.30	5.357%	$238.4229	$238.42	$238.40	$238.40
Purchase #6	$166.96	13.285%	$189.1406	$189.14	$189.15	$189.10
Purchase #7	$62.48	6.646%	$66.6324	$66.63	$66.65	$66.60
7 purchase totals =	$859.26		$938.5415	$938.54	$938.55	$938.50