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 $54.88   11.336%   $61.1012   $61.10   $61.10   $61.10  
  Purchase #2 $156.54   12.533%   $176.1592   $176.16   $176.15   $176.20  
  Purchase #3 $229.26   7.356%   $246.1244   $246.12   $246.10   $246.10  
  Purchase #4 $176.79   3.434%   $182.861   $182.86   $182.85   $182.90  
  Purchase #5 $100.98   9.813%   $110.8892   $110.89   $110.90   $110.90  
  Purchase #6 $183.59   10.790%   $203.3994   $203.40   $203.40   $203.40  
  Purchase #7 $31.38   7.258%   $33.6576   $33.66   $33.65   $33.70  
  7 purchase totals = $933.42       $1,014.1920   $1,014.19   $1,014.15   $1,014.30