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 $214.89   12.522%   $241.7985   $241.80   $241.80   $241.80  
  Purchase #2 $106.69   6.154%   $113.2557   $113.26   $113.25   $113.30  
  Purchase #3 $229.74   12.475%   $258.4001   $258.40   $258.40   $258.40  
  Purchase #4 $53.93   8.756%   $58.6521   $58.65   $58.65   $58.70  
  Purchase #5 $211.38   6.745%   $225.6376   $225.64   $225.65   $225.60  
  Purchase #6 $157.45   12.582%   $177.2604   $177.26   $177.25   $177.30  
  Purchase #7 $110.97   8.326%   $120.2094   $120.21   $120.20   $120.20  
  7 purchase totals = $1,085.05       $1,195.2138   $1,195.22   $1,195.20   $1,195.30