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 $88.74   7.486%   $95.3831   $95.38   $95.40   $95.40  
  Purchase #2 $34.79   12.416%   $39.1095   $39.11   $39.10   $39.10  
  Purchase #3 $185.55   10.431%   $204.9047   $204.90   $204.90   $204.90  
  Purchase #4 $150.28   13.670%   $170.8233   $170.82   $170.80   $170.80  
  Purchase #5 $237.59   5.835%   $251.4534   $251.45   $251.45   $251.50  
  Purchase #6 $71.62   3.169%   $73.8896   $73.89   $73.90   $73.90  
  Purchase #7 $224.74   3.216%   $231.9676   $231.97   $231.95   $232.00  
  7 purchase totals = $993.31       $1,067.5312   $1,067.52   $1,067.50   $1,067.60