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 $41.77   5.282%   $43.9763   $43.98   $44.00   $44.00  
  Purchase #2 $23.84   5.715%   $25.2025   $25.20   $25.20   $25.20  
  Purchase #3 $71.51   8.789%   $77.795   $77.80   $77.80   $77.80  
  Purchase #4 $180.55   7.754%   $194.5498   $194.55   $194.55   $194.50  
  Purchase #5 $198.70   13.127%   $224.7833   $224.78   $224.80   $224.80  
  Purchase #6 $47.96   3.788%   $49.7767   $49.78   $49.80   $49.80  
  Purchase #7 $133.44   9.115%   $145.6031   $145.60   $145.60   $145.60  
  7 purchase totals = $697.77       $761.6867   $761.69   $761.75   $761.70