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 $156.26   11.102%   $173.608   $173.61   $173.60   $173.60  
  Purchase #2 $52.61   12.108%   $58.98   $58.98   $59.00   $59.00  
  Purchase #3 $238.56   8.726%   $259.3767   $259.38   $259.40   $259.40  
  Purchase #4 $153.54   7.837%   $165.5729   $165.57   $165.55   $165.60  
  Purchase #5 $202.44   4.529%   $211.6085   $211.61   $211.60   $211.60  
  Purchase #6 $157.52   7.585%   $169.4679   $169.47   $169.45   $169.50  
  Purchase #7 $79.87   9.865%   $87.7492   $87.75   $87.75   $87.70  
  7 purchase totals = $1,040.80       $1,126.3632   $1,126.37   $1,126.35   $1,126.40