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 $195.81   5.674%   $206.9203   $206.92   $206.90   $206.90  
  Purchase #2 $159.95   5.148%   $168.1842   $168.18   $168.20   $168.20  
  Purchase #3 $5.29   5.519%   $5.582   $5.58   $5.60   $5.60  
  Purchase #4 $143.72   9.424%   $157.2642   $157.26   $157.25   $157.30  
  Purchase #5 $169.98   5.496%   $179.3221   $179.32   $179.30   $179.30  
  Purchase #6 $180.49   3.527%   $186.8559   $186.86   $186.85   $186.90  
  Purchase #7 $182.94   3.608%   $189.5405   $189.54   $189.55   $189.50  
  7 purchase totals = $1,038.18       $1,093.6692   $1,093.66   $1,093.65   $1,093.70