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 $173.74   12.586%   $195.6069   $195.61   $195.60   $195.60  
  Purchase #2 $97.97   6.569%   $104.4056   $104.41   $104.40   $104.40  
  Purchase #3 $179.48   13.143%   $203.0691   $203.07   $203.05   $203.10  
  Purchase #4 $67.26   9.411%   $73.5898   $73.59   $73.60   $73.60  
  Purchase #5 $184.75   10.784%   $204.6734   $204.67   $204.65   $204.70  
  Purchase #6 $168.94   4.320%   $176.2382   $176.24   $176.25   $176.20  
  Purchase #7 $55.87   5.304%   $58.8333   $58.83   $58.85   $58.80  
  7 purchase totals = $928.01       $1,016.4163   $1,016.42   $1,016.40   $1,016.40