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 $168.82   4.244%   $175.9847   $175.98   $176.00   $176.00  
  Purchase #2 $33.36   3.769%   $34.6173   $34.62   $34.60   $34.60  
  Purchase #3 $160.53   10.579%   $177.5125   $177.51   $177.50   $177.50  
  Purchase #4 $151.26   3.698%   $156.8536   $156.85   $156.85   $156.90  
  Purchase #5 $161.58   7.869%   $174.2947   $174.29   $174.30   $174.30  
  Purchase #6 $236.93   11.276%   $263.6462   $263.65   $263.65   $263.60  
  Purchase #7 $62.46   10.358%   $68.9296   $68.93   $68.95   $68.90  
  7 purchase totals = $974.94       $1,051.8386   $1,051.83   $1,051.85   $1,051.80