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 $54.50   13.296%   $61.7463   $61.75   $61.75   $61.70  
  Purchase #2 $175.38   11.319%   $195.2313   $195.23   $195.25   $195.20  
  Purchase #3 $39.57   13.650%   $44.9713   $44.97   $44.95   $45.00  
  Purchase #4 $6.40   6.115%   $6.7914   $6.79   $6.80   $6.80  
  Purchase #5 $17.67   6.264%   $18.7768   $18.78   $18.80   $18.80  
  Purchase #6 $238.72   3.465%   $246.9916   $246.99   $247.00   $247.00  
  Purchase #7 $194.41   9.534%   $212.945   $212.95   $212.95   $212.90  
  7 purchase totals = $726.65       $787.4537   $787.46   $787.50   $787.40