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 $181.44   8.494%   $196.8515   $196.85   $196.85   $196.90  
  Purchase #2 $149.90   10.502%   $165.6425   $165.64   $165.65   $165.60  
  Purchase #3 $50.26   3.476%   $52.007   $52.01   $52.00   $52.00  
  Purchase #4 $183.33   11.817%   $204.9941   $204.99   $205.00   $205.00  
  Purchase #5 $144.63   11.803%   $161.7007   $161.70   $161.70   $161.70  
  Purchase #6 $153.51   8.293%   $166.2406   $166.24   $166.25   $166.20  
  Purchase #7 $245.26   7.584%   $263.8605   $263.86   $263.85   $263.90  
  7 purchase totals = $1,108.33       $1,211.2969   $1,211.29   $1,211.30   $1,211.30