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 $205.68   8.781%   $223.7408   $223.74   $223.75   $223.70  
  Purchase #2 $190.27   3.207%   $196.372   $196.37   $196.35   $196.40  
  Purchase #3 $32.51   7.518%   $34.9541   $34.95   $34.95   $35.00  
  Purchase #4 $212.43   10.405%   $234.5333   $234.53   $234.55   $234.50  
  Purchase #5 $182.44   6.455%   $194.2165   $194.22   $194.20   $194.20  
  Purchase #6 $82.87   6.352%   $88.1339   $88.13   $88.15   $88.10  
  Purchase #7 $129.69   6.655%   $138.3209   $138.32   $138.30   $138.30  
  7 purchase totals = $1,035.89       $1,110.2715   $1,110.26   $1,110.25   $1,110.20