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 $87.51   5.826%   $92.6083   $92.61   $92.60   $92.60  
  Purchase #2 $111.90   13.721%   $127.2538   $127.25   $127.25   $127.30  
  Purchase #3 $75.57   10.249%   $83.3152   $83.32   $83.30   $83.30  
  Purchase #4 $126.73   9.380%   $138.6173   $138.62   $138.60   $138.60  
  Purchase #5 $213.69   3.402%   $220.9597   $220.96   $220.95   $221.00  
  Purchase #6 $191.36   5.513%   $201.9097   $201.91   $201.90   $201.90  
  Purchase #7 $191.43   3.667%   $198.4497   $198.45   $198.45   $198.40  
  7 purchase totals = $998.19       $1,063.1137   $1,063.12   $1,063.05   $1,063.10