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 $193.54   5.409%   $204.0086   $204.01   $204.00   $204.00  
  Purchase #2 $250.62   5.618%   $264.6998   $264.70   $264.70   $264.70  
  Purchase #3 $203.26   5.395%   $214.2259   $214.23   $214.25   $214.20  
  Purchase #4 $36.48   5.687%   $38.5546   $38.55   $38.55   $38.60  
  Purchase #5 $232.86   9.210%   $254.3064   $254.31   $254.30   $254.30  
  Purchase #6 $221.36   11.747%   $247.3632   $247.36   $247.35   $247.40  
  Purchase #7 $32.62   9.584%   $35.7463   $35.75   $35.75   $35.70  
  7 purchase totals = $1,170.74       $1,258.9048   $1,258.91   $1,258.90   $1,258.90