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 $58.47   6.342%   $62.1782   $62.18   $62.20   $62.20  
  Purchase #2 $30.40   7.140%   $32.5706   $32.57   $32.55   $32.60  
  Purchase #3 $10.67   6.607%   $11.375   $11.38   $11.40   $11.40  
  Purchase #4 $174.90   3.638%   $181.2629   $181.26   $181.25   $181.30  
  Purchase #5 $47.59   7.398%   $51.1107   $51.11   $51.10   $51.10  
  Purchase #6 $226.80   5.232%   $238.6662   $238.67   $238.65   $238.70  
  Purchase #7 $178.62   3.592%   $185.036   $185.04   $185.05   $185.00  
  7 purchase totals = $727.45       $762.1996   $762.21   $762.20   $762.30