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 $63.33   13.440%   $71.8416   $71.84   $71.85   $71.80  
  Purchase #2 $237.52   5.446%   $250.4553   $250.46   $250.45   $250.50  
  Purchase #3 $212.63   8.485%   $230.6717   $230.67   $230.65   $230.70  
  Purchase #4 $238.51   10.221%   $262.8881   $262.89   $262.90   $262.90  
  Purchase #5 $121.28   6.358%   $128.991   $128.99   $129.00   $129.00  
  Purchase #6 $48.65   12.531%   $54.7463   $54.75   $54.75   $54.70  
  Purchase #7 $180.81   6.725%   $192.9695   $192.97   $192.95   $193.00  
  7 purchase totals = $1,102.73       $1,192.5635   $1,192.57   $1,192.55   $1,192.60