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 $244.46   7.155%   $261.9511   $261.95   $261.95   $262.00  
  Purchase #2 $84.67   13.133%   $95.7897   $95.79   $95.80   $95.80  
  Purchase #3 $184.33   9.466%   $201.7787   $201.78   $201.80   $201.80  
  Purchase #4 $179.98   11.144%   $200.037   $200.04   $200.05   $200.00  
  Purchase #5 $49.35   12.779%   $55.6564   $55.66   $55.65   $55.70  
  Purchase #6 $177.52   6.288%   $188.6825   $188.68   $188.70   $188.70  
  Purchase #7 $128.43   9.694%   $140.88   $140.88   $140.90   $140.90  
  7 purchase totals = $1,048.74       $1,144.7754   $1,144.78   $1,144.85   $1,144.90