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 $175.63   11.707%   $196.191   $196.19   $196.20   $196.20  
  Purchase #2 $223.36   4.608%   $233.6524   $233.65   $233.65   $233.70  
  Purchase #3 $66.87   9.293%   $73.0842   $73.08   $73.10   $73.10  
  Purchase #4 $125.79   5.344%   $132.5122   $132.51   $132.50   $132.50  
  Purchase #5 $67.83   3.797%   $70.4055   $70.41   $70.40   $70.40  
  Purchase #6 $120.84   13.227%   $136.8235   $136.82   $136.80   $136.80  
  Purchase #7 $165.48   3.708%   $171.616   $171.62   $171.60   $171.60  
  7 purchase totals = $945.80       $1,014.2848   $1,014.28   $1,014.25   $1,014.30