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 $87.82   8.710%   $95.4691   $95.47   $95.45   $95.50  
  Purchase #2 $54.59   8.750%   $59.3666   $59.37   $59.35   $59.40  
  Purchase #3 $83.48   4.669%   $87.3777   $87.38   $87.40   $87.40  
  Purchase #4 $220.74   9.536%   $241.7898   $241.79   $241.80   $241.80  
  Purchase #5 $171.61   7.460%   $184.4121   $184.41   $184.40   $184.40  
  Purchase #6 $161.66   7.456%   $173.7134   $173.71   $173.70   $173.70  
  Purchase #7 $113.96   4.155%   $118.695   $118.70   $118.70   $118.70  
  7 purchase totals = $893.86       $960.8237   $960.83   $960.80   $960.90