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 $244.28   6.510%   $260.1826   $260.18   $260.20   $260.20  
  Purchase #2 $143.52   7.353%   $154.073   $154.07   $154.05   $154.10  
  Purchase #3 $70.54   6.764%   $75.3113   $75.31   $75.30   $75.30  
  Purchase #4 $205.99   11.498%   $229.6747   $229.67   $229.65   $229.70  
  Purchase #5 $246.88   7.351%   $265.0281   $265.03   $265.05   $265.00  
  Purchase #6 $126.38   13.514%   $143.459   $143.46   $143.45   $143.50  
  Purchase #7 $62.54   6.558%   $66.6414   $66.64   $66.65   $66.60  
  7 purchase totals = $1,100.13       $1,194.3701   $1,194.36   $1,194.35   $1,194.40