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 $215.97   13.559%   $245.2534   $245.25   $245.25   $245.30  
  Purchase #2 $53.48   3.319%   $55.255   $55.26   $55.25   $55.30  
  Purchase #3 $63.54   11.833%   $71.0587   $71.06   $71.05   $71.10  
  Purchase #4 $120.82   10.501%   $133.5073   $133.51   $133.50   $133.50  
  Purchase #5 $246.28   10.704%   $272.6418   $272.64   $272.65   $272.60  
  Purchase #6 $156.73   13.749%   $178.2788   $178.28   $178.30   $178.30  
  Purchase #7 $197.80   6.700%   $211.0526   $211.05   $211.05   $211.10  
  7 purchase totals = $1,054.62       $1,167.0476   $1,167.05   $1,167.05   $1,167.20