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 $237.60   11.249%   $264.3276   $264.33   $264.35   $264.30  
  Purchase #2 $240.83   5.585%   $254.2804   $254.28   $254.30   $254.30  
  Purchase #3 $48.49   5.372%   $51.0949   $51.09   $51.10   $51.10  
  Purchase #4 $235.42   10.830%   $260.916   $260.92   $260.90   $260.90  
  Purchase #5 $49.38   10.790%   $54.7081   $54.71   $54.70   $54.70  
  Purchase #6 $232.50   4.706%   $243.4415   $243.44   $243.45   $243.40  
  Purchase #7 $31.75   6.709%   $33.8801   $33.88   $33.90   $33.90  
  7 purchase totals = $1,075.97       $1,162.6486   $1,162.65   $1,162.70   $1,162.60