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 $32.82   4.658%   $34.3488   $34.35   $34.35   $34.30  
  Purchase #2 $112.82   11.737%   $126.0617   $126.06   $126.05   $126.10  
  Purchase #3 $94.27   8.171%   $101.9728   $101.97   $101.95   $102.00  
  Purchase #4 $232.57   8.545%   $252.4431   $252.44   $252.45   $252.40  
  Purchase #5 $120.38   10.789%   $133.3678   $133.37   $133.35   $133.40  
  Purchase #6 $190.72   11.329%   $212.3267   $212.33   $212.35   $212.30  
  Purchase #7 $145.67   8.836%   $158.5414   $158.54   $158.55   $158.50  
  7 purchase totals = $929.25       $1,019.0623   $1,019.06   $1,019.05   $1,019.00