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 $193.66   9.797%   $212.6329   $212.63   $212.65   $212.60  
  Purchase #2 $13.87   3.351%   $14.3348   $14.33   $14.35   $14.30  
  Purchase #3 $24.59   5.811%   $26.0189   $26.02   $26.00   $26.00  
  Purchase #4 $237.82   5.709%   $251.3971   $251.40   $251.40   $251.40  
  Purchase #5 $159.79   4.343%   $166.7297   $166.73   $166.75   $166.70  
  Purchase #6 $68.39   9.458%   $74.8583   $74.86   $74.85   $74.90  
  Purchase #7 $156.46   3.128%   $161.3541   $161.35   $161.35   $161.40  
  7 purchase totals = $854.58       $907.3258   $907.32   $907.35   $907.30