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 $39.26   5.869%   $41.5642   $41.56   $41.55   $41.60  
  Purchase #2 $224.43   3.448%   $232.1683   $232.17   $232.15   $232.20  
  Purchase #3 $148.60   3.617%   $153.9749   $153.97   $153.95   $154.00  
  Purchase #4 $250.58   3.782%   $260.0569   $260.06   $260.05   $260.10  
  Purchase #5 $246.36   3.742%   $255.5788   $255.58   $255.60   $255.60  
  Purchase #6 $167.84   4.532%   $175.4465   $175.45   $175.45   $175.40  
  Purchase #7 $216.79   7.473%   $232.9907   $232.99   $233.00   $233.00  
  7 purchase totals = $1,293.86       $1,351.7803   $1,351.78   $1,351.75   $1,351.90