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 $58.62   5.793%   $62.0159   $62.02   $62.00   $62.00  
  Purchase #2 $228.57   13.692%   $259.8658   $259.87   $259.85   $259.90  
  Purchase #3 $99.98   5.169%   $105.148   $105.15   $105.15   $105.10  
  Purchase #4 $224.29   12.106%   $251.4425   $251.44   $251.45   $251.40  
  Purchase #5 $164.92   8.257%   $178.5374   $178.54   $178.55   $178.50  
  Purchase #6 $129.98   6.567%   $138.5158   $138.52   $138.50   $138.50  
  Purchase #7 $187.60   8.704%   $203.9287   $203.93   $203.95   $203.90  
  7 purchase totals = $1,093.96       $1,199.4541   $1,199.47   $1,199.45   $1,199.30