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 $85.72   10.858%   $95.0275   $95.03   $95.05   $95.00  
  Purchase #2 $81.73   12.514%   $91.9577   $91.96   $91.95   $92.00  
  Purchase #3 $147.29   8.160%   $159.3089   $159.31   $159.30   $159.30  
  Purchase #4 $219.78   7.603%   $236.4899   $236.49   $236.50   $236.50  
  Purchase #5 $44.55   10.595%   $49.2701   $49.27   $49.25   $49.30  
  Purchase #6 $39.91   12.598%   $44.9379   $44.94   $44.95   $44.90  
  Purchase #7 $250.49   11.356%   $278.9356   $278.94   $278.95   $278.90  
  7 purchase totals = $869.47       $955.9276   $955.94   $955.95   $955.90