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 $46.69   12.177%   $52.3754   $52.38   $52.40   $52.40  
  Purchase #2 $189.64   3.707%   $196.67   $196.67   $196.65   $196.70  
  Purchase #3 $218.52   6.421%   $232.5512   $232.55   $232.55   $232.60  
  Purchase #4 $197.46   9.595%   $216.4063   $216.41   $216.40   $216.40  
  Purchase #5 $226.90   8.683%   $246.6017   $246.60   $246.60   $246.60  
  Purchase #6 $118.82   11.428%   $132.3987   $132.40   $132.40   $132.40  
  Purchase #7 $205.73   5.506%   $217.0575   $217.06   $217.05   $217.10  
  7 purchase totals = $1,203.76       $1,294.0608   $1,294.07   $1,294.05   $1,294.20