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 $85.82   11.550%   $95.7322   $95.73   $95.75   $95.70  
  Purchase #2 $172.98   6.124%   $183.5733   $183.57   $183.55   $183.60  
  Purchase #3 $241.89   4.842%   $253.6023   $253.60   $253.60   $253.60  
  Purchase #4 $149.49   7.201%   $160.2548   $160.25   $160.25   $160.30  
  Purchase #5 $53.30   4.696%   $55.803   $55.80   $55.80   $55.80  
  Purchase #6 $21.26   8.576%   $23.0833   $23.08   $23.10   $23.10  
  Purchase #7 $161.42   9.758%   $177.1714   $177.17   $177.15   $177.20  
  7 purchase totals = $886.16       $949.2203   $949.20   $949.20   $949.30