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 $143.87   5.445%   $151.7037   $151.70   $151.70   $151.70  
  Purchase #2 $231.88   4.738%   $242.8665   $242.87   $242.85   $242.90  
  Purchase #3 $160.89   6.493%   $171.3366   $171.34   $171.35   $171.30  
  Purchase #4 $66.64   11.181%   $74.091   $74.09   $74.10   $74.10  
  Purchase #5 $113.51   11.251%   $126.281   $126.28   $126.30   $126.30  
  Purchase #6 $161.45   7.454%   $173.4845   $173.48   $173.50   $173.50  
  Purchase #7 $144.80   7.568%   $155.7585   $155.76   $155.75   $155.80  
  7 purchase totals = $1,023.04       $1,095.5218   $1,095.52   $1,095.55   $1,095.60