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 $61.37   5.679%   $64.8552   $64.86   $64.85   $64.90  
  Purchase #2 $223.93   5.126%   $235.4087   $235.41   $235.40   $235.40  
  Purchase #3 $52.56   6.178%   $55.8072   $55.81   $55.80   $55.80  
  Purchase #4 $84.56   4.352%   $88.2401   $88.24   $88.25   $88.20  
  Purchase #5 $50.93   11.533%   $56.8038   $56.80   $56.80   $56.80  
  Purchase #6 $234.70   7.339%   $251.9246   $251.92   $251.90   $251.90  
  Purchase #7 $187.65   4.308%   $195.734   $195.73   $195.75   $195.70  
  7 purchase totals = $895.70       $948.7736   $948.77   $948.75   $948.70