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 $240.28   10.432%   $265.346   $265.35   $265.35   $265.30  
  Purchase #2 $108.49   7.728%   $116.8741   $116.87   $116.85   $116.90  
  Purchase #3 $123.70   6.541%   $131.7912   $131.79   $131.80   $131.80  
  Purchase #4 $192.71   7.354%   $206.8819   $206.88   $206.90   $206.90  
  Purchase #5 $230.30   7.509%   $247.5932   $247.59   $247.60   $247.60  
  Purchase #6 $155.26   9.297%   $169.6945   $169.69   $169.70   $169.70  
  Purchase #7 $13.52   3.398%   $13.9794   $13.98   $14.00   $14.00  
  7 purchase totals = $1,064.26       $1,152.1603   $1,152.15   $1,152.20   $1,152.20