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 $173.50   12.759%   $195.6369   $195.64   $195.65   $195.60  
  Purchase #2 $85.85   9.103%   $93.6649   $93.66   $93.65   $93.70  
  Purchase #3 $137.71   9.610%   $150.9439   $150.94   $150.95   $150.90  
  Purchase #4 $108.32   12.426%   $121.7798   $121.78   $121.80   $121.80  
  Purchase #5 $137.63   10.253%   $151.7412   $151.74   $151.75   $151.70  
  Purchase #6 $122.62   11.519%   $136.7446   $136.74   $136.75   $136.70  
  Purchase #7 $150.89   8.698%   $164.0144   $164.01   $164.00   $164.00  
  7 purchase totals = $916.52       $1,014.5257   $1,014.51   $1,014.55   $1,014.40