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 $85.55   11.856%   $95.6928   $95.69   $95.70   $95.70  
  Purchase #2 $203.82   11.379%   $227.0127   $227.01   $227.00   $227.00  
  Purchase #3 $198.96   13.388%   $225.5968   $225.60   $225.60   $225.60  
  Purchase #4 $65.61   7.605%   $70.5996   $70.60   $70.60   $70.60  
  Purchase #5 $241.98   10.653%   $267.7581   $267.76   $267.75   $267.80  
  Purchase #6 $105.36   6.407%   $112.1104   $112.11   $112.10   $112.10  
  Purchase #7 $214.42   7.709%   $230.9496   $230.95   $230.95   $230.90  
  7 purchase totals = $1,115.70       $1,229.7200   $1,229.72   $1,229.70   $1,229.70