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 $60.57   10.586%   $66.9819   $66.98   $67.00   $67.00  
  Purchase #2 $205.92   6.173%   $218.6314   $218.63   $218.65   $218.60  
  Purchase #3 $149.81   10.815%   $166.012   $166.01   $166.00   $166.00  
  Purchase #4 $174.25   13.183%   $197.2214   $197.22   $197.20   $197.20  
  Purchase #5 $152.27   4.854%   $159.6612   $159.66   $159.65   $159.70  
  Purchase #6 $105.58   13.713%   $120.0582   $120.06   $120.05   $120.10  
  Purchase #7 $186.79   8.151%   $202.0153   $202.02   $202.00   $202.00  
  7 purchase totals = $1,035.19       $1,130.5814   $1,130.58   $1,130.55   $1,130.60