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 $136.28   10.628%   $150.7638   $150.76   $150.75   $150.80  
  Purchase #2 $184.34   8.488%   $199.9868   $199.99   $200.00   $200.00  
  Purchase #3 $33.52   8.178%   $36.2613   $36.26   $36.25   $36.30  
  Purchase #4 $250.85   6.639%   $267.5039   $267.50   $267.50   $267.50  
  Purchase #5 $175.96   5.385%   $185.4354   $185.44   $185.45   $185.40  
  Purchase #6 $162.59   8.288%   $176.0655   $176.07   $176.05   $176.10  
  Purchase #7 $14.95   6.862%   $15.9759   $15.98   $16.00   $16.00  
  7 purchase totals = $958.49       $1,031.9926   $1,032.00   $1,032.00   $1,032.10