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 $74.49   4.660%   $77.9612   $77.96   $77.95   $78.00  
  Purchase #2 $89.37   4.454%   $93.3505   $93.35   $93.35   $93.40  
  Purchase #3 $191.82   4.813%   $201.0523   $201.05   $201.05   $201.10  
  Purchase #4 $13.98   3.103%   $14.4138   $14.41   $14.40   $14.40  
  Purchase #5 $77.52   6.729%   $82.7363   $82.74   $82.75   $82.70  
  Purchase #6 $92.72   11.193%   $103.0981   $103.10   $103.10   $103.10  
  Purchase #7 $167.81   7.316%   $180.087   $180.09   $180.10   $180.10  
  7 purchase totals = $707.71       $752.6992   $752.70   $752.70   $752.80