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 $84.32   13.578%   $95.769   $95.77   $95.75   $95.80  
  Purchase #2 $109.81   8.138%   $118.7463   $118.75   $118.75   $118.70  
  Purchase #3 $105.70   10.647%   $116.9539   $116.95   $116.95   $117.00  
  Purchase #4 $41.92   7.173%   $44.9269   $44.93   $44.95   $44.90  
  Purchase #5 $191.85   7.779%   $206.774   $206.77   $206.75   $206.80  
  Purchase #6 $224.27   6.284%   $238.3631   $238.36   $238.35   $238.40  
  Purchase #7 $82.96   9.484%   $90.8279   $90.83   $90.85   $90.80  
  7 purchase totals = $840.83       $912.3611   $912.36   $912.35   $912.40