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 $69.70   3.211%   $71.9381   $71.94   $71.95   $71.90  
  Purchase #2 $9.85   5.239%   $10.366   $10.37   $10.35   $10.40  
  Purchase #3 $71.63   12.594%   $80.6511   $80.65   $80.65   $80.70  
  Purchase #4 $245.27   6.829%   $262.0195   $262.02   $262.00   $262.00  
  Purchase #5 $132.94   9.182%   $145.1466   $145.15   $145.15   $145.10  
  Purchase #6 $112.47   10.841%   $124.6629   $124.66   $124.65   $124.70  
  Purchase #7 $59.37   8.325%   $64.3126   $64.31   $64.30   $64.30  
  7 purchase totals = $701.23       $759.0968   $759.10   $759.05   $759.10