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 $187.68   7.232%   $201.253   $201.25   $201.25   $201.30  
  Purchase #2 $192.90   7.298%   $206.9778   $206.98   $207.00   $207.00  
  Purchase #3 $18.58   6.267%   $19.7444   $19.74   $19.75   $19.70  
  Purchase #4 $212.38   7.609%   $228.54   $228.54   $228.55   $228.50  
  Purchase #5 $6.34   6.160%   $6.7305   $6.73   $6.75   $6.70  
  Purchase #6 $82.65   5.679%   $87.3437   $87.34   $87.35   $87.30  
  Purchase #7 $195.69   12.271%   $219.7031   $219.70   $219.70   $219.70  
  7 purchase totals = $896.22       $970.2925   $970.28   $970.35   $970.20