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 $177.63   10.372%   $196.0538   $196.05   $196.05   $196.10  
  Purchase #2 $91.35   5.558%   $96.4272   $96.43   $96.45   $96.40  
  Purchase #3 $68.81   11.618%   $76.8043   $76.80   $76.80   $76.80  
  Purchase #4 $84.27   5.143%   $88.604   $88.60   $88.60   $88.60  
  Purchase #5 $244.75   7.339%   $262.7122   $262.71   $262.70   $262.70  
  Purchase #6 $134.53   11.626%   $150.1705   $150.17   $150.15   $150.20  
  Purchase #7 $162.52   6.430%   $172.97   $172.97   $172.95   $173.00  
  7 purchase totals = $963.86       $1,043.7420   $1,043.73   $1,043.70   $1,043.80