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 $65.98   12.565%   $74.2704   $74.27   $74.25   $74.30  
  Purchase #2 $55.61   4.579%   $58.1564   $58.16   $58.15   $58.20  
  Purchase #3 $99.72   3.198%   $102.909   $102.91   $102.90   $102.90  
  Purchase #4 $98.72   3.265%   $101.9432   $101.94   $101.95   $101.90  
  Purchase #5 $226.25   5.348%   $238.3499   $238.35   $238.35   $238.30  
  Purchase #6 $234.59   12.674%   $264.3219   $264.32   $264.30   $264.30  
  Purchase #7 $187.35   12.671%   $211.0891   $211.09   $211.10   $211.10  
  7 purchase totals = $968.22       $1,051.0399   $1,051.04   $1,051.00   $1,051.00