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 $58.59   6.302%   $62.2823   $62.28   $62.30   $62.30  
  Purchase #2 $24.47   6.710%   $26.1119   $26.11   $26.10   $26.10  
  Purchase #3 $162.64   4.639%   $170.1849   $170.18   $170.20   $170.20  
  Purchase #4 $184.78   8.541%   $200.5621   $200.56   $200.55   $200.60  
  Purchase #5 $154.85   7.199%   $165.9977   $166.00   $166.00   $166.00  
  Purchase #6 $203.28   11.239%   $226.1266   $226.13   $226.15   $226.10  
  Purchase #7 $61.72   9.734%   $67.7278   $67.73   $67.75   $67.70  
  7 purchase totals = $850.33       $918.9933   $918.99   $919.05   $919.00