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 $181.92   12.600%   $204.8419   $204.84   $204.85   $204.80  
  Purchase #2 $206.89   4.342%   $215.8732   $215.87   $215.85   $215.90  
  Purchase #3 $235.61   12.358%   $264.7267   $264.73   $264.75   $264.70  
  Purchase #4 $245.48   4.558%   $256.669   $256.67   $256.65   $256.70  
  Purchase #5 $42.85   4.472%   $44.7663   $44.77   $44.75   $44.80  
  Purchase #6 $169.37   6.519%   $180.4112   $180.41   $180.40   $180.40  
  Purchase #7 $186.93   7.199%   $200.3871   $200.39   $200.40   $200.40  
  7 purchase totals = $1,269.05       $1,367.6754   $1,367.68   $1,367.65   $1,367.70