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 $86.74   8.587%   $94.1884   $94.19   $94.20   $94.20  
  Purchase #2 $132.48   9.322%   $144.8298   $144.83   $144.85   $144.80  
  Purchase #3 $219.65   13.664%   $249.663   $249.66   $249.65   $249.70  
  Purchase #4 $224.86   8.778%   $244.5982   $244.60   $244.60   $244.60  
  Purchase #5 $80.41   8.240%   $87.0358   $87.04   $87.05   $87.00  
  Purchase #6 $16.28   3.120%   $16.7879   $16.79   $16.80   $16.80  
  Purchase #7 $204.96   3.737%   $212.6194   $212.62   $212.60   $212.60  
  7 purchase totals = $965.38       $1,049.7225   $1,049.73   $1,049.75   $1,049.70