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 $59.83   4.800%   $62.7018   $62.70   $62.70   $62.70  
  Purchase #2 $228.93   3.731%   $237.4714   $237.47   $237.45   $237.50  
  Purchase #3 $148.45   8.418%   $160.9465   $160.95   $160.95   $160.90  
  Purchase #4 $168.31   13.363%   $190.8013   $190.80   $190.80   $190.80  
  Purchase #5 $150.96   9.792%   $165.742   $165.74   $165.75   $165.70  
  Purchase #6 $32.92   6.397%   $35.0259   $35.03   $35.05   $35.00  
  Purchase #7 $246.70   9.530%   $270.2105   $270.21   $270.20   $270.20  
  7 purchase totals = $1,036.10       $1,122.8994   $1,122.90   $1,122.90   $1,122.80