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 $185.71   8.245%   $201.0218   $201.02   $201.00   $201.00  
  Purchase #2 $151.64   10.121%   $166.9875   $166.99   $167.00   $167.00  
  Purchase #3 $162.66   10.412%   $179.5962   $179.60   $179.60   $179.60  
  Purchase #4 $149.27   6.226%   $158.5636   $158.56   $158.55   $158.60  
  Purchase #5 $53.39   3.470%   $55.2426   $55.24   $55.25   $55.20  
  Purchase #6 $123.42   12.568%   $138.9314   $138.93   $138.95   $138.90  
  Purchase #7 $242.54   5.231%   $255.2273   $255.23   $255.25   $255.20  
  7 purchase totals = $1,068.63       $1,155.5704   $1,155.57   $1,155.60   $1,155.50