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 $246.85   6.762%   $263.542   $263.54   $263.55   $263.50  
  Purchase #2 $136.73   6.738%   $145.9429   $145.94   $145.95   $145.90  
  Purchase #3 $61.72   11.267%   $68.674   $68.67   $68.65   $68.70  
  Purchase #4 $129.74   3.185%   $133.8722   $133.87   $133.85   $133.90  
  Purchase #5 $190.38   6.798%   $203.322   $203.32   $203.30   $203.30  
  Purchase #6 $238.50   6.562%   $254.1504   $254.15   $254.15   $254.20  
  Purchase #7 $43.96   5.828%   $46.522   $46.52   $46.50   $46.50  
  7 purchase totals = $1,047.88       $1,116.0255   $1,116.01   $1,115.95   $1,116.00