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 $224.98   5.656%   $237.7049   $237.70   $237.70   $237.70  
  Purchase #2 $187.47   3.850%   $194.6876   $194.69   $194.70   $194.70  
  Purchase #3 $119.50   6.112%   $126.8038   $126.80   $126.80   $126.80  
  Purchase #4 $161.99   6.641%   $172.7478   $172.75   $172.75   $172.70  
  Purchase #5 $50.77   5.767%   $53.6979   $53.70   $53.70   $53.70  
  Purchase #6 $124.78   3.154%   $128.7156   $128.72   $128.70   $128.70  
  Purchase #7 $88.60   4.163%   $92.2884   $92.29   $92.30   $92.30  
  7 purchase totals = $958.09       $1,006.6460   $1,006.65   $1,006.65   $1,006.60