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 $71.67   4.663%   $75.012   $75.01   $75.00   $75.00  
  Purchase #2 $194.44   12.303%   $218.362   $218.36   $218.35   $218.40  
  Purchase #3 $23.97   10.782%   $26.5544   $26.55   $26.55   $26.60  
  Purchase #4 $243.67   11.373%   $271.3826   $271.38   $271.40   $271.40  
  Purchase #5 $93.45   11.470%   $104.1687   $104.17   $104.15   $104.20  
  Purchase #6 $192.44   12.742%   $216.9607   $216.96   $216.95   $217.00  
  Purchase #7 $228.79   5.398%   $241.1401   $241.14   $241.15   $241.10  
  7 purchase totals = $1,048.43       $1,153.5805   $1,153.57   $1,153.55   $1,153.70