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 $102.65   10.263%   $113.185   $113.19   $113.20   $113.20  
  Purchase #2 $191.78   10.216%   $211.3722   $211.37   $211.35   $211.40  
  Purchase #3 $63.48   4.796%   $66.5245   $66.52   $66.50   $66.50  
  Purchase #4 $203.49   5.556%   $214.7959   $214.80   $214.80   $214.80  
  Purchase #5 $164.68   6.198%   $174.8869   $174.89   $174.90   $174.90  
  Purchase #6 $100.33   12.238%   $112.6084   $112.61   $112.60   $112.60  
  Purchase #7 $79.25   5.463%   $83.5794   $83.58   $83.60   $83.60  
  7 purchase totals = $905.66       $976.9523   $976.96   $976.95   $977.00