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 $162.86   7.304%   $174.7553   $174.76   $174.75   $174.80  
  Purchase #2 $194.76   3.338%   $201.2611   $201.26   $201.25   $201.30  
  Purchase #3 $106.58   11.425%   $118.7568   $118.76   $118.75   $118.80  
  Purchase #4 $58.85   7.846%   $63.4674   $63.47   $63.45   $63.50  
  Purchase #5 $83.87   6.751%   $89.5321   $89.53   $89.55   $89.50  
  Purchase #6 $231.58   5.310%   $243.8769   $243.88   $243.90   $243.90  
  Purchase #7 $75.98   8.709%   $82.5971   $82.60   $82.60   $82.60  
  7 purchase totals = $914.48       $974.2467   $974.26   $974.25   $974.40