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 $76.75   13.874%   $87.3983   $87.40   $87.40   $87.40  
  Purchase #2 $106.78   9.403%   $116.8205   $116.82   $116.80   $116.80  
  Purchase #3 $236.31   12.247%   $265.2509   $265.25   $265.25   $265.30  
  Purchase #4 $182.38   7.808%   $196.6202   $196.62   $196.60   $196.60  
  Purchase #5 $134.92   4.480%   $140.9644   $140.96   $140.95   $141.00  
  Purchase #6 $212.96   8.247%   $230.5228   $230.52   $230.50   $230.50  
  Purchase #7 $213.68   4.761%   $223.8533   $223.85   $223.85   $223.90  
  7 purchase totals = $1,163.78       $1,261.4304   $1,261.42   $1,261.35   $1,261.50