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 $69.51   10.224%   $76.6167   $76.62   $76.60   $76.60  
  Purchase #2 $217.34   9.657%   $238.3285   $238.33   $238.35   $238.30  
  Purchase #3 $174.56   13.398%   $197.9475   $197.95   $197.95   $197.90  
  Purchase #4 $60.50   12.665%   $68.1623   $68.16   $68.15   $68.20  
  Purchase #5 $80.78   3.574%   $83.6671   $83.67   $83.65   $83.70  
  Purchase #6 $198.66   10.137%   $218.7982   $218.80   $218.80   $218.80  
  Purchase #7 $217.91   10.261%   $240.2697   $240.27   $240.25   $240.30  
  7 purchase totals = $1,019.26       $1,123.7900   $1,123.80   $1,123.75   $1,123.80