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 $185.71   11.370%   $206.8252   $206.83   $206.85   $206.80  
  Purchase #2 $165.53   9.866%   $181.8612   $181.86   $181.85   $181.90  
  Purchase #3 $187.36   5.543%   $197.7454   $197.75   $197.75   $197.70  
  Purchase #4 $176.62   3.376%   $182.5827   $182.58   $182.60   $182.60  
  Purchase #5 $169.62   6.338%   $180.3705   $180.37   $180.35   $180.40  
  Purchase #6 $90.70   4.726%   $94.9865   $94.99   $95.00   $95.00  
  Purchase #7 $6.98   9.462%   $7.6404   $7.64   $7.65   $7.60  
  7 purchase totals = $982.52       $1,052.0119   $1,052.02   $1,052.05   $1,052.00