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 $24.52   7.786%   $26.4291   $26.43   $26.45   $26.40  
  Purchase #2 $152.82   10.716%   $169.1962   $169.20   $169.20   $169.20  
  Purchase #3 $160.28   12.781%   $180.7654   $180.77   $180.75   $180.80  
  Purchase #4 $183.27   7.691%   $197.3653   $197.37   $197.35   $197.40  
  Purchase #5 $211.28   4.151%   $220.0502   $220.05   $220.05   $220.10  
  Purchase #6 $70.78   8.610%   $76.8742   $76.87   $76.85   $76.90  
  Purchase #7 $173.29   11.565%   $193.331   $193.33   $193.35   $193.30  
  7 purchase totals = $976.24       $1,064.0114   $1,064.02   $1,064.00   $1,064.10