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 $49.82   4.543%   $52.0833   $52.08   $52.10   $52.10  
  Purchase #2 $178.79   8.158%   $193.3757   $193.38   $193.40   $193.40  
  Purchase #3 $147.75   4.428%   $154.2924   $154.29   $154.30   $154.30  
  Purchase #4 $246.82   8.641%   $268.1477   $268.15   $268.15   $268.10  
  Purchase #5 $201.93   7.221%   $216.5114   $216.51   $216.50   $216.50  
  Purchase #6 $115.47   3.135%   $119.09   $119.09   $119.10   $119.10  
  Purchase #7 $190.36   7.364%   $204.3781   $204.38   $204.40   $204.40  
  7 purchase totals = $1,130.94       $1,207.8786   $1,207.88   $1,207.95   $1,207.90