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 $222.44   4.699%   $232.8925   $232.89   $232.90   $232.90  
  Purchase #2 $248.26   7.633%   $267.2097   $267.21   $267.20   $267.20  
  Purchase #3 $58.27   7.727%   $62.7725   $62.77   $62.75   $62.80  
  Purchase #4 $118.92   5.618%   $125.6009   $125.60   $125.60   $125.60  
  Purchase #5 $78.80   12.783%   $88.873   $88.87   $88.85   $88.90  
  Purchase #6 $232.90   7.510%   $250.3908   $250.39   $250.40   $250.40  
  Purchase #7 $94.27   6.631%   $100.521   $100.52   $100.50   $100.50  
  7 purchase totals = $1,053.86       $1,128.2604   $1,128.25   $1,128.20   $1,128.30