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 $92.44   13.644%   $105.0525   $105.05   $105.05   $105.10  
  Purchase #2 $153.43   13.219%   $173.7119   $173.71   $173.70   $173.70  
  Purchase #3 $223.26   12.777%   $251.7859   $251.79   $251.80   $251.80  
  Purchase #4 $44.64   6.752%   $47.6541   $47.65   $47.65   $47.70  
  Purchase #5 $5.64   7.447%   $6.06   $6.06   $6.05   $6.10  
  Purchase #6 $232.37   11.767%   $259.713   $259.71   $259.70   $259.70  
  Purchase #7 $209.27   4.318%   $218.3063   $218.31   $218.30   $218.30  
  7 purchase totals = $961.05       $1,062.2837   $1,062.28   $1,062.25   $1,062.40