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 $90.79   7.280%   $97.3995   $97.40   $97.40   $97.40  
  Purchase #2 $22.78   6.447%   $24.2486   $24.25   $24.25   $24.20  
  Purchase #3 $234.76   8.578%   $254.8977   $254.90   $254.90   $254.90  
  Purchase #4 $167.70   11.873%   $187.611   $187.61   $187.60   $187.60  
  Purchase #5 $185.52   6.673%   $197.8997   $197.90   $197.90   $197.90  
  Purchase #6 $124.80   4.837%   $130.8366   $130.84   $130.85   $130.80  
  Purchase #7 $198.77   6.120%   $210.9347   $210.93   $210.95   $210.90  
  7 purchase totals = $1,025.12       $1,103.8278   $1,103.83   $1,103.85   $1,103.70