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 $53.81   5.755%   $56.9068   $56.91   $56.90   $56.90  
  Purchase #2 $115.98   13.608%   $131.7626   $131.76   $131.75   $131.80  
  Purchase #3 $217.98   4.686%   $228.1945   $228.19   $228.20   $228.20  
  Purchase #4 $84.68   13.450%   $96.0695   $96.07   $96.05   $96.10  
  Purchase #5 $80.36   7.322%   $86.244   $86.24   $86.25   $86.20  
  Purchase #6 $63.62   5.862%   $67.3494   $67.35   $67.35   $67.30  
  Purchase #7 $197.84   5.691%   $209.0991   $209.10   $209.10   $209.10  
  7 purchase totals = $814.27       $875.6259   $875.62   $875.60   $875.60