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 $192.60   11.540%   $214.826   $214.83   $214.85   $214.80  
  Purchase #2 $179.42   12.347%   $201.573   $201.57   $201.55   $201.60  
  Purchase #3 $94.94   7.266%   $101.8383   $101.84   $101.85   $101.80  
  Purchase #4 $189.58   12.490%   $213.2585   $213.26   $213.25   $213.30  
  Purchase #5 $188.97   10.780%   $209.341   $209.34   $209.35   $209.30  
  Purchase #6 $223.75   8.689%   $243.1916   $243.19   $243.20   $243.20  
  Purchase #7 $64.82   10.544%   $71.6546   $71.65   $71.65   $71.70  
  7 purchase totals = $1,134.08       $1,255.6830   $1,255.68   $1,255.70   $1,255.70