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 $151.96   5.480%   $160.2874   $160.29   $160.30   $160.30  
  Purchase #2 $176.78   9.714%   $193.9524   $193.95   $193.95   $194.00  
  Purchase #3 $164.84   7.789%   $177.6794   $177.68   $177.70   $177.70  
  Purchase #4 $225.26   4.112%   $234.5227   $234.52   $234.50   $234.50  
  Purchase #5 $63.48   5.736%   $67.1212   $67.12   $67.10   $67.10  
  Purchase #6 $149.46   13.860%   $170.1752   $170.18   $170.20   $170.20  
  Purchase #7 $24.47   5.767%   $25.8812   $25.88   $25.90   $25.90  
  7 purchase totals = $956.25       $1,029.6195   $1,029.62   $1,029.65   $1,029.70