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 $60.34   4.288%   $62.9274   $62.93   $62.95   $62.90  
  Purchase #2 $148.30   9.219%   $161.9718   $161.97   $161.95   $162.00  
  Purchase #3 $224.58   3.691%   $232.8692   $232.87   $232.85   $232.90  
  Purchase #4 $56.79   7.521%   $61.0612   $61.06   $61.05   $61.10  
  Purchase #5 $82.43   3.390%   $85.2244   $85.22   $85.20   $85.20  
  Purchase #6 $227.77   11.373%   $253.6743   $253.67   $253.65   $253.70  
  Purchase #7 $137.33   12.413%   $154.3768   $154.38   $154.40   $154.40  
  7 purchase totals = $937.54       $1,012.1051   $1,012.10   $1,012.05   $1,012.20