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 $116.90   11.430%   $130.2617   $130.26   $130.25   $130.30  
  Purchase #2 $61.38   6.287%   $65.239   $65.24   $65.25   $65.20  
  Purchase #3 $60.76   11.219%   $67.5767   $67.58   $67.60   $67.60  
  Purchase #4 $246.36   7.261%   $264.2482   $264.25   $264.25   $264.20  
  Purchase #5 $246.79   7.390%   $265.0278   $265.03   $265.05   $265.00  
  Purchase #6 $52.31   7.477%   $56.2212   $56.22   $56.20   $56.20  
  Purchase #7 $192.65   9.779%   $211.4892   $211.49   $211.50   $211.50  
  7 purchase totals = $977.15       $1,060.0638   $1,060.07   $1,060.10   $1,060.00