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 $195.67   3.264%   $202.0567   $202.06   $202.05   $202.10  
  Purchase #2 $184.99   10.503%   $204.4195   $204.42   $204.40   $204.40  
  Purchase #3 $126.67   8.216%   $137.0772   $137.08   $137.10   $137.10  
  Purchase #4 $191.41   8.221%   $207.1458   $207.15   $207.15   $207.10  
  Purchase #5 $199.31   11.348%   $221.9277   $221.93   $221.95   $221.90  
  Purchase #6 $151.34   10.150%   $166.701   $166.70   $166.70   $166.70  
  Purchase #7 $175.75   10.664%   $194.492   $194.49   $194.50   $194.50  
  7 purchase totals = $1,225.14       $1,333.8199   $1,333.83   $1,333.85   $1,333.80