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 $212.59   9.180%   $232.1058   $232.11   $232.10   $232.10  
  Purchase #2 $165.80   7.673%   $178.5218   $178.52   $178.50   $178.50  
  Purchase #3 $76.48   7.177%   $81.969   $81.97   $81.95   $82.00  
  Purchase #4 $219.59   9.177%   $239.7418   $239.74   $239.75   $239.70  
  Purchase #5 $231.77   3.672%   $240.2806   $240.28   $240.30   $240.30  
  Purchase #6 $47.56   8.562%   $51.6321   $51.63   $51.65   $51.60  
  Purchase #7 $93.45   13.237%   $105.82   $105.82   $105.80   $105.80  
  7 purchase totals = $1,047.24       $1,130.0711   $1,130.07   $1,130.05   $1,130.00