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 $87.86   8.253%   $95.1111   $95.11   $95.10   $95.10  
  Purchase #2 $158.29   10.195%   $174.4277   $174.43   $174.45   $174.40  
  Purchase #3 $110.54   8.518%   $119.9558   $119.96   $119.95   $120.00  
  Purchase #4 $24.82   4.817%   $26.0156   $26.02   $26.00   $26.00  
  Purchase #5 $179.99   13.640%   $204.5406   $204.54   $204.55   $204.50  
  Purchase #6 $27.41   9.701%   $30.069   $30.07   $30.05   $30.10  
  Purchase #7 $126.40   6.835%   $135.0394   $135.04   $135.05   $135.00  
  7 purchase totals = $715.31       $785.1592   $785.17   $785.15   $785.10