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 $58.55   4.702%   $61.303   $61.30   $61.30   $61.30  
  Purchase #2 $24.62   10.475%   $27.1989   $27.20   $27.20   $27.20  
  Purchase #3 $195.80   10.416%   $216.1945   $216.19   $216.20   $216.20  
  Purchase #4 $169.71   11.466%   $189.1689   $189.17   $189.15   $189.20  
  Purchase #5 $241.91   5.811%   $255.9674   $255.97   $255.95   $256.00  
  Purchase #6 $22.27   6.831%   $23.7913   $23.79   $23.80   $23.80  
  Purchase #7 $20.47   4.846%   $21.462   $21.46   $21.45   $21.50  
  7 purchase totals = $733.33       $795.0860   $795.08   $795.05   $795.20