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 $66.86   3.572%   $69.2482   $69.25   $69.25   $69.20  
  Purchase #2 $203.46   5.355%   $214.3553   $214.36   $214.35   $214.40  
  Purchase #3 $31.79   12.546%   $35.7784   $35.78   $35.80   $35.80  
  Purchase #4 $20.82   4.107%   $21.6751   $21.68   $21.70   $21.70  
  Purchase #5 $211.71   9.606%   $232.0469   $232.05   $232.05   $232.00  
  Purchase #6 $111.45   7.284%   $119.568   $119.57   $119.55   $119.60  
  Purchase #7 $150.60   11.591%   $168.056   $168.06   $168.05   $168.10  
  7 purchase totals = $796.69       $860.7279   $860.75   $860.75   $860.80