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 $219.88   5.847%   $232.7364   $232.74   $232.75   $232.70  
  Purchase #2 $44.97   4.207%   $46.8619   $46.86   $46.85   $46.90  
  Purchase #3 $114.39   3.571%   $118.4749   $118.47   $118.45   $118.50  
  Purchase #4 $10.86   6.580%   $11.5746   $11.57   $11.55   $11.60  
  Purchase #5 $205.46   6.713%   $219.2525   $219.25   $219.25   $219.30  
  Purchase #6 $104.55   4.541%   $109.2976   $109.30   $109.30   $109.30  
  Purchase #7 $138.69   13.552%   $157.4853   $157.49   $157.50   $157.50  
  7 purchase totals = $838.80       $895.6832   $895.68   $895.65   $895.80