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 $223.87   6.558%   $238.5514   $238.55   $238.55   $238.60  
  Purchase #2 $72.28   5.289%   $76.1029   $76.10   $76.10   $76.10  
  Purchase #3 $248.71   7.145%   $266.4803   $266.48   $266.50   $266.50  
  Purchase #4 $209.98   8.603%   $228.0446   $228.04   $228.05   $228.00  
  Purchase #5 $54.92   9.160%   $59.9507   $59.95   $59.95   $60.00  
  Purchase #6 $193.72   5.418%   $204.2157   $204.22   $204.20   $204.20  
  Purchase #7 $20.90   7.121%   $22.3883   $22.39   $22.40   $22.40  
  7 purchase totals = $1,024.38       $1,095.7339   $1,095.73   $1,095.75   $1,095.80