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 $48.87   5.791%   $51.7001   $51.70   $51.70   $51.70  
  Purchase #2 $153.34   6.625%   $163.4988   $163.50   $163.50   $163.50  
  Purchase #3 $118.32   12.866%   $133.5431   $133.54   $133.55   $133.50  
  Purchase #4 $114.98   13.129%   $130.0757   $130.08   $130.10   $130.10  
  Purchase #5 $198.87   12.661%   $224.0489   $224.05   $224.05   $224.00  
  Purchase #6 $203.55   5.246%   $214.2282   $214.23   $214.25   $214.20  
  Purchase #7 $216.49   9.569%   $237.2059   $237.21   $237.20   $237.20  
  7 purchase totals = $1,054.42       $1,154.3007   $1,154.31   $1,154.35   $1,154.20