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 $105.75   12.738%   $119.2204   $119.22   $119.20   $119.20  
  Purchase #2 $61.39   8.494%   $66.6045   $66.60   $66.60   $66.60  
  Purchase #3 $189.43   3.795%   $196.6189   $196.62   $196.60   $196.60  
  Purchase #4 $74.36   7.867%   $80.2099   $80.21   $80.20   $80.20  
  Purchase #5 $182.97   11.831%   $204.6172   $204.62   $204.60   $204.60  
  Purchase #6 $192.46   10.717%   $213.0859   $213.09   $213.10   $213.10  
  Purchase #7 $243.95   11.392%   $271.7408   $271.74   $271.75   $271.70  
  7 purchase totals = $1,050.31       $1,152.0976   $1,152.10   $1,152.05   $1,152.00