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 $187.26   7.729%   $201.7333   $201.73   $201.75   $201.70  
  Purchase #2 $97.31   6.516%   $103.6507   $103.65   $103.65   $103.70  
  Purchase #3 $102.26   10.420%   $112.9155   $112.92   $112.90   $112.90  
  Purchase #4 $244.89   11.110%   $272.0973   $272.10   $272.10   $272.10  
  Purchase #5 $81.64   5.280%   $85.9506   $85.95   $85.95   $86.00  
  Purchase #6 $230.37   9.631%   $252.5569   $252.56   $252.55   $252.60  
  Purchase #7 $31.88   5.338%   $33.5818   $33.58   $33.60   $33.60  
  7 purchase totals = $975.61       $1,062.4861   $1,062.49   $1,062.50   $1,062.60