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 $219.66   7.302%   $235.6996   $235.70   $235.70   $235.70  
  Purchase #2 $189.56   7.111%   $203.0396   $203.04   $203.05   $203.00  
  Purchase #3 $8.66   6.596%   $9.2312   $9.23   $9.25   $9.20  
  Purchase #4 $54.58   12.577%   $61.4445   $61.44   $61.45   $61.40  
  Purchase #5 $82.60   6.197%   $87.7187   $87.72   $87.70   $87.70  
  Purchase #6 $188.62   8.474%   $204.6037   $204.60   $204.60   $204.60  
  Purchase #7 $211.71   4.698%   $221.6561   $221.66   $221.65   $221.70  
  7 purchase totals = $955.39       $1,023.3934   $1,023.39   $1,023.40   $1,023.30