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 $56.26   4.241%   $58.646   $58.65   $58.65   $58.60  
  Purchase #2 $65.38   9.721%   $71.7356   $71.74   $71.75   $71.70  
  Purchase #3 $118.79   5.123%   $124.8756   $124.88   $124.90   $124.90  
  Purchase #4 $141.58   6.232%   $150.4033   $150.40   $150.40   $150.40  
  Purchase #5 $232.52   5.570%   $245.4714   $245.47   $245.45   $245.50  
  Purchase #6 $88.76   3.567%   $91.9261   $91.93   $91.95   $91.90  
  Purchase #7 $174.27   4.430%   $181.9902   $181.99   $182.00   $182.00  
  7 purchase totals = $877.56       $925.0482   $925.06   $925.10   $925.00