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 $87.56   9.184%   $95.6015   $95.60   $95.60   $95.60  
  Purchase #2 $229.70   4.760%   $240.6337   $240.63   $240.65   $240.60  
  Purchase #3 $218.25   12.408%   $245.3305   $245.33   $245.35   $245.30  
  Purchase #4 $104.38   3.249%   $107.7713   $107.77   $107.75   $107.80  
  Purchase #5 $35.46   8.418%   $38.445   $38.45   $38.45   $38.40  
  Purchase #6 $51.52   4.424%   $53.7992   $53.80   $53.80   $53.80  
  Purchase #7 $213.74   6.833%   $228.3449   $228.34   $228.35   $228.30  
  7 purchase totals = $940.61       $1,009.9261   $1,009.92   $1,009.95   $1,009.80