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 $78.66   10.553%   $86.961   $86.96   $86.95   $87.00  
  Purchase #2 $17.31   4.480%   $18.0855   $18.09   $18.10   $18.10  
  Purchase #3 $181.77   5.640%   $192.0218   $192.02   $192.00   $192.00  
  Purchase #4 $66.94   9.199%   $73.0978   $73.10   $73.10   $73.10  
  Purchase #5 $191.73   7.346%   $205.8145   $205.81   $205.80   $205.80  
  Purchase #6 $116.48   8.427%   $126.2958   $126.30   $126.30   $126.30  
  Purchase #7 $189.36   7.547%   $203.651   $203.65   $203.65   $203.70  
  7 purchase totals = $842.25       $905.9274   $905.93   $905.90   $906.00