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 $85.95   9.761%   $94.3396   $94.34   $94.35   $94.30  
  Purchase #2 $187.44   11.825%   $209.6048   $209.60   $209.60   $209.60  
  Purchase #3 $245.41   3.708%   $254.5098   $254.51   $254.50   $254.50  
  Purchase #4 $59.69   9.255%   $65.2143   $65.21   $65.20   $65.20  
  Purchase #5 $204.49   8.653%   $222.1845   $222.18   $222.20   $222.20  
  Purchase #6 $5.46   3.406%   $5.646   $5.65   $5.65   $5.60  
  Purchase #7 $201.26   3.329%   $207.9599   $207.96   $207.95   $208.00  
  7 purchase totals = $989.70       $1,059.4589   $1,059.45   $1,059.45   $1,059.40