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 $177.66   8.380%   $192.5479   $192.55   $192.55   $192.50  
  Purchase #2 $97.90   9.615%   $107.3131   $107.31   $107.30   $107.30  
  Purchase #3 $156.75   11.532%   $174.8264   $174.83   $174.85   $174.80  
  Purchase #4 $13.70   3.805%   $14.2213   $14.22   $14.20   $14.20  
  Purchase #5 $110.28   6.379%   $117.3148   $117.31   $117.30   $117.30  
  Purchase #6 $212.27   6.352%   $225.7534   $225.75   $225.75   $225.80  
  Purchase #7 $176.79   8.395%   $191.6315   $191.63   $191.65   $191.60  
  7 purchase totals = $945.35       $1,023.6084   $1,023.60   $1,023.60   $1,023.50