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 $58.65   6.457%   $62.437   $62.44   $62.45   $62.40  
  Purchase #2 $56.32   11.298%   $62.683   $62.68   $62.70   $62.70  
  Purchase #3 $108.94   13.198%   $123.3179   $123.32   $123.30   $123.30  
  Purchase #4 $206.29   13.214%   $233.5492   $233.55   $233.55   $233.50  
  Purchase #5 $151.96   7.495%   $163.3494   $163.35   $163.35   $163.30  
  Purchase #6 $82.52   7.366%   $88.5984   $88.60   $88.60   $88.60  
  Purchase #7 $15.38   11.699%   $17.1793   $17.18   $17.20   $17.20  
  7 purchase totals = $680.06       $751.1142   $751.12   $751.15   $751.00