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 $213.53   5.126%   $224.4755   $224.48   $224.50   $224.50  
  Purchase #2 $239.60   11.670%   $267.5613   $267.56   $267.55   $267.60  
  Purchase #3 $162.81   10.607%   $180.0793   $180.08   $180.10   $180.10  
  Purchase #4 $156.90   11.266%   $174.5764   $174.58   $174.60   $174.60  
  Purchase #5 $51.98   9.528%   $56.9327   $56.93   $56.95   $56.90  
  Purchase #6 $23.53   9.605%   $25.7901   $25.79   $25.80   $25.80  
  Purchase #7 $84.44   13.850%   $96.1349   $96.13   $96.15   $96.10  
  7 purchase totals = $932.79       $1,025.5502   $1,025.55   $1,025.65   $1,025.60