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 $87.74   8.581%   $95.269   $95.27   $95.25   $95.30  
  Purchase #2 $184.39   6.425%   $196.2371   $196.24   $196.25   $196.20  
  Purchase #3 $58.87   10.782%   $65.2174   $65.22   $65.20   $65.20  
  Purchase #4 $16.38   10.683%   $18.1299   $18.13   $18.15   $18.10  
  Purchase #5 $205.94   13.533%   $233.8099   $233.81   $233.80   $233.80  
  Purchase #6 $161.65   13.589%   $183.6166   $183.62   $183.60   $183.60  
  Purchase #7 $180.91   7.538%   $194.547   $194.55   $194.55   $194.50  
  7 purchase totals = $895.88       $986.8269   $986.84   $986.80   $986.70