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	$62.91	4.422%	$65.6919	$65.69	$65.70	$65.70
Purchase #2	$202.47	5.224%	$213.047	$213.05	$213.05	$213.00
Purchase #3	$146.29	12.712%	$164.8864	$164.89	$164.90	$164.90
Purchase #4	$88.96	7.810%	$95.9078	$95.91	$95.90	$95.90
Purchase #5	$133.42	7.828%	$143.8641	$143.86	$143.85	$143.90
Purchase #6	$122.61	9.498%	$134.2555	$134.26	$134.25	$134.30
Purchase #7	$213.93	13.268%	$242.3142	$242.31	$242.30	$242.30
7 purchase totals =	$970.59		$1,059.9669	$1,059.97	$1,059.95	$1,060.00