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 $62.70   8.606%   $68.096   $68.10   $68.10   $68.10  
  Purchase #2 $82.60   12.588%   $92.9977   $93.00   $93.00   $93.00  
  Purchase #3 $170.36   12.445%   $191.5613   $191.56   $191.55   $191.60  
  Purchase #4 $169.46   4.644%   $177.3297   $177.33   $177.35   $177.30  
  Purchase #5 $111.93   8.241%   $121.1542   $121.15   $121.15   $121.20  
  Purchase #6 $179.46   11.835%   $200.6991   $200.70   $200.70   $200.70  
  Purchase #7 $153.79   3.519%   $159.2019   $159.20   $159.20   $159.20  
  7 purchase totals = $930.30       $1,011.0399   $1,011.04   $1,011.05   $1,011.10