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 $195.62   8.235%   $211.7293   $211.73   $211.75   $211.70  
  Purchase #2 $218.43   10.494%   $241.352   $241.35   $241.35   $241.40  
  Purchase #3 $10.44   11.713%   $11.6628   $11.66   $11.65   $11.70  
  Purchase #4 $64.35   10.639%   $71.1962   $71.20   $71.20   $71.20  
  Purchase #5 $5.70   4.581%   $5.9611   $5.96   $5.95   $6.00  
  Purchase #6 $182.65   3.777%   $189.5487   $189.55   $189.55   $189.50  
  Purchase #7 $51.89   8.352%   $56.2239   $56.22   $56.20   $56.20  
  7 purchase totals = $729.08       $787.6740   $787.67   $787.65   $787.70