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	$64.48	11.238%	$71.7263	$71.73	$71.75	$71.70
Purchase #2	$155.57	8.667%	$169.0533	$169.05	$169.05	$169.10
Purchase #3	$27.88	13.187%	$31.5565	$31.56	$31.55	$31.60
Purchase #4	$193.94	13.684%	$220.4787	$220.48	$220.50	$220.50
Purchase #5	$104.92	9.477%	$114.8633	$114.86	$114.85	$114.90
Purchase #6	$224.52	4.481%	$234.5807	$234.58	$234.60	$234.60
Purchase #7	$145.97	10.701%	$161.5902	$161.59	$161.60	$161.60
7 purchase totals =	$917.28		$1,003.8490	$1,003.85	$1,003.90	$1,004.00