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 $155.35   7.658%   $167.2467   $167.25   $167.25   $167.20  
  Purchase #2 $31.65   8.413%   $34.3127   $34.31   $34.30   $34.30  
  Purchase #3 $176.55   10.409%   $194.9271   $194.93   $194.95   $194.90  
  Purchase #4 $168.75   12.676%   $190.1408   $190.14   $190.15   $190.10  
  Purchase #5 $183.41   11.286%   $204.1097   $204.11   $204.10   $204.10  
  Purchase #6 $206.64   5.481%   $217.9659   $217.97   $217.95   $218.00  
  Purchase #7 $55.26   6.127%   $58.6458   $58.65   $58.65   $58.60  
  7 purchase totals = $977.61       $1,067.3487   $1,067.36   $1,067.35   $1,067.20