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 $189.58   7.340%   $203.4952   $203.50   $203.50   $203.50  
  Purchase #2 $43.73   5.479%   $46.126   $46.13   $46.15   $46.10  
  Purchase #3 $154.68   12.747%   $174.3971   $174.40   $174.40   $174.40  
  Purchase #4 $111.49   7.376%   $119.7135   $119.71   $119.70   $119.70  
  Purchase #5 $227.85   5.392%   $240.1357   $240.14   $240.15   $240.10  
  Purchase #6 $213.45   4.731%   $223.5483   $223.55   $223.55   $223.50  
  Purchase #7 $146.33   9.137%   $159.7002   $159.70   $159.70   $159.70  
  7 purchase totals = $1,087.11       $1,167.1160   $1,167.13   $1,167.15   $1,167.00