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 $224.29   5.102%   $235.7333   $235.73   $235.75   $235.70  
  Purchase #2 $211.97   5.614%   $223.87   $223.87   $223.85   $223.90  
  Purchase #3 $160.33   4.743%   $167.9345   $167.93   $167.95   $167.90  
  Purchase #4 $36.59   6.163%   $38.845   $38.85   $38.85   $38.80  
  Purchase #5 $130.93   5.664%   $138.3459   $138.35   $138.35   $138.30  
  Purchase #6 $184.70   12.745%   $208.24   $208.24   $208.25   $208.20  
  Purchase #7 $125.72   12.315%   $141.2024   $141.20   $141.20   $141.20  
  7 purchase totals = $1,074.53       $1,154.1711   $1,154.17   $1,154.20   $1,154.00