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 $143.26   4.844%   $150.1995   $150.20   $150.20   $150.20  
  Purchase #2 $146.92   6.841%   $156.9708   $156.97   $156.95   $157.00  
  Purchase #3 $167.87   8.808%   $182.656   $182.66   $182.65   $182.70  
  Purchase #4 $203.84   5.385%   $214.8168   $214.82   $214.80   $214.80  
  Purchase #5 $98.72   5.623%   $104.271   $104.27   $104.25   $104.30  
  Purchase #6 $215.90   13.192%   $244.3815   $244.38   $244.40   $244.40  
  Purchase #7 $99.97   12.340%   $112.3063   $112.31   $112.30   $112.30  
  7 purchase totals = $1,076.48       $1,165.6019   $1,165.61   $1,165.55   $1,165.70