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 $228.36   7.506%   $245.5007   $245.50   $245.50   $245.50  
  Purchase #2 $84.75   13.490%   $96.1828   $96.18   $96.20   $96.20  
  Purchase #3 $209.96   5.491%   $221.4889   $221.49   $221.50   $221.50  
  Purchase #4 $91.56   13.565%   $103.9801   $103.98   $104.00   $104.00  
  Purchase #5 $227.42   3.360%   $235.0613   $235.06   $235.05   $235.10  
  Purchase #6 $110.47   4.411%   $115.3428   $115.34   $115.35   $115.30  
  Purchase #7 $54.45   7.807%   $58.7009   $58.70   $58.70   $58.70  
  7 purchase totals = $1,006.97       $1,076.2575   $1,076.25   $1,076.30   $1,076.30