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 $88.26   7.261%   $94.6686   $94.67   $94.65   $94.70  
  Purchase #2 $217.97   4.786%   $228.402   $228.40   $228.40   $228.40  
  Purchase #3 $82.71   7.231%   $88.6908   $88.69   $88.70   $88.70  
  Purchase #4 $17.72   11.615%   $19.7782   $19.78   $19.80   $19.80  
  Purchase #5 $250.82   5.391%   $264.3417   $264.34   $264.35   $264.30  
  Purchase #6 $91.74   3.611%   $95.0527   $95.05   $95.05   $95.10  
  Purchase #7 $165.84   11.774%   $185.366   $185.37   $185.35   $185.40  
  7 purchase totals = $915.06       $976.3000   $976.30   $976.30   $976.40