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 $35.44   6.258%   $37.6578   $37.66   $37.65   $37.70  
  Purchase #2 $174.61   11.191%   $194.1506   $194.15   $194.15   $194.20  
  Purchase #3 $80.44   8.506%   $87.2822   $87.28   $87.30   $87.30  
  Purchase #4 $152.59   7.674%   $164.2998   $164.30   $164.30   $164.30  
  Purchase #5 $108.77   6.665%   $116.0195   $116.02   $116.00   $116.00  
  Purchase #6 $95.33   6.739%   $101.7543   $101.75   $101.75   $101.80  
  Purchase #7 $249.79   5.637%   $263.8707   $263.87   $263.85   $263.90  
  7 purchase totals = $896.97       $965.0349   $965.03   $965.00   $965.20