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 $250.97   4.380%   $261.9625   $261.96   $261.95   $262.00  
  Purchase #2 $18.54   9.369%   $20.277   $20.28   $20.30   $20.30  
  Purchase #3 $211.42   4.459%   $220.8472   $220.85   $220.85   $220.80  
  Purchase #4 $119.82   10.110%   $131.9338   $131.93   $131.95   $131.90  
  Purchase #5 $96.85   9.652%   $106.198   $106.20   $106.20   $106.20  
  Purchase #6 $225.69   11.562%   $251.7843   $251.78   $251.80   $251.80  
  Purchase #7 $90.79   9.752%   $99.6438   $99.64   $99.65   $99.60  
  7 purchase totals = $1,014.08       $1,092.6466   $1,092.64   $1,092.70   $1,092.60