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 $92.72   3.244%   $95.7278   $95.73   $95.75   $95.70  
  Purchase #2 $182.46   8.441%   $197.8614   $197.86   $197.85   $197.90  
  Purchase #3 $9.78   6.107%   $10.3773   $10.38   $10.40   $10.40  
  Purchase #4 $181.95   10.788%   $201.5788   $201.58   $201.60   $201.60  
  Purchase #5 $10.86   3.842%   $11.2772   $11.28   $11.30   $11.30  
  Purchase #6 $239.32   8.150%   $258.8246   $258.82   $258.80   $258.80  
  Purchase #7 $229.80   10.513%   $253.9589   $253.96   $253.95   $254.00  
  7 purchase totals = $946.89       $1,029.6060   $1,029.61   $1,029.65   $1,029.70