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 $214.78   8.709%   $233.4852   $233.49   $233.50   $233.50  
  Purchase #2 $24.88   6.354%   $26.4609   $26.46   $26.45   $26.50  
  Purchase #3 $218.84   6.281%   $232.5853   $232.59   $232.60   $232.60  
  Purchase #4 $132.80   9.624%   $145.5807   $145.58   $145.60   $145.60  
  Purchase #5 $180.92   13.475%   $205.299   $205.30   $205.30   $205.30  
  Purchase #6 $40.69   9.766%   $44.6638   $44.66   $44.65   $44.70  
  Purchase #7 $162.88   6.780%   $173.9233   $173.92   $173.90   $173.90  
  7 purchase totals = $975.79       $1,061.9982   $1,062.00   $1,062.00   $1,062.10