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 $55.45   11.183%   $61.651   $61.65   $61.65   $61.70  
  Purchase #2 $194.53   9.744%   $213.485   $213.49   $213.50   $213.50  
  Purchase #3 $81.85   8.212%   $88.5715   $88.57   $88.55   $88.60  
  Purchase #4 $163.73   9.184%   $178.767   $178.77   $178.75   $178.80  
  Purchase #5 $195.66   4.725%   $204.9049   $204.90   $204.90   $204.90  
  Purchase #6 $238.94   8.440%   $259.1065   $259.11   $259.10   $259.10  
  Purchase #7 $132.85   6.594%   $141.6101   $141.61   $141.60   $141.60  
  7 purchase totals = $1,063.01       $1,148.0960   $1,148.10   $1,148.05   $1,148.20