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 $66.52   8.869%   $72.4197   $72.42   $72.40   $72.40  
  Purchase #2 $211.91   11.325%   $235.9088   $235.91   $235.90   $235.90  
  Purchase #3 $219.66   10.192%   $242.0477   $242.05   $242.05   $242.00  
  Purchase #4 $66.99   7.793%   $72.2105   $72.21   $72.20   $72.20  
  Purchase #5 $228.67   4.450%   $238.8458   $238.85   $238.85   $238.80  
  Purchase #6 $22.46   13.269%   $25.4402   $25.44   $25.45   $25.40  
  Purchase #7 $156.33   12.796%   $176.334   $176.33   $176.35   $176.30  
  7 purchase totals = $972.54       $1,063.2067   $1,063.21   $1,063.20   $1,063.00