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 $86.28   10.126%   $95.0167   $95.02   $95.00   $95.00  
  Purchase #2 $85.55   9.457%   $93.6405   $93.64   $93.65   $93.60  
  Purchase #3 $157.34   7.719%   $169.4851   $169.49   $169.50   $169.50  
  Purchase #4 $183.47   11.584%   $204.7232   $204.72   $204.70   $204.70  
  Purchase #5 $130.97   11.336%   $145.8168   $145.82   $145.80   $145.80  
  Purchase #6 $106.84   3.479%   $110.557   $110.56   $110.55   $110.60  
  Purchase #7 $226.36   10.420%   $249.9467   $249.95   $249.95   $249.90  
  7 purchase totals = $976.81       $1,069.1860   $1,069.20   $1,069.15   $1,069.10