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 $134.69   5.873%   $142.6003   $142.60   $142.60   $142.60  
  Purchase #2 $84.76   12.622%   $95.4584   $95.46   $95.45   $95.50  
  Purchase #3 $185.88   6.282%   $197.557   $197.56   $197.55   $197.60  
  Purchase #4 $216.53   5.743%   $228.9653   $228.97   $228.95   $229.00  
  Purchase #5 $102.80   4.427%   $107.351   $107.35   $107.35   $107.40  
  Purchase #6 $205.31   12.264%   $230.4892   $230.49   $230.50   $230.50  
  Purchase #7 $162.88   9.765%   $178.7852   $178.79   $178.80   $178.80  
  7 purchase totals = $1,092.85       $1,181.2064   $1,181.22   $1,181.20   $1,181.40