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 $88.38   5.477%   $93.2206   $93.22   $93.20   $93.20  
  Purchase #2 $246.68   10.578%   $272.7738   $272.77   $272.75   $272.80  
  Purchase #3 $173.77   10.422%   $191.8803   $191.88   $191.90   $191.90  
  Purchase #4 $9.76   3.417%   $10.0935   $10.09   $10.10   $10.10  
  Purchase #5 $211.73   7.508%   $227.6267   $227.63   $227.65   $227.60  
  Purchase #6 $152.64   7.107%   $163.4881   $163.49   $163.50   $163.50  
  Purchase #7 $70.66   4.464%   $73.8143   $73.81   $73.80   $73.80  
  7 purchase totals = $953.62       $1,032.8973   $1,032.89   $1,032.90   $1,032.90