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 $67.32   10.124%   $74.1355   $74.14   $74.15   $74.10  
  Purchase #2 $136.54   11.551%   $152.3117   $152.31   $152.30   $152.30  
  Purchase #3 $234.72   3.155%   $242.1254   $242.13   $242.15   $242.10  
  Purchase #4 $123.29   13.185%   $139.5458   $139.55   $139.55   $139.50  
  Purchase #5 $224.27   3.709%   $232.5882   $232.59   $232.60   $232.60  
  Purchase #6 $184.56   8.194%   $199.6828   $199.68   $199.70   $199.70  
  Purchase #7 $26.56   5.713%   $28.0774   $28.08   $28.10   $28.10  
  7 purchase totals = $997.26       $1,068.4668   $1,068.48   $1,068.55   $1,068.40