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 $113.51   10.570%   $125.508   $125.51   $125.50   $125.50  
  Purchase #2 $64.52   8.573%   $70.0513   $70.05   $70.05   $70.10  
  Purchase #3 $98.53   4.563%   $103.0259   $103.03   $103.05   $103.00  
  Purchase #4 $208.80   13.250%   $236.466   $236.47   $236.45   $236.50  
  Purchase #5 $171.66   13.522%   $194.8719   $194.87   $194.85   $194.90  
  Purchase #6 $160.72   4.184%   $167.4445   $167.44   $167.45   $167.40  
  Purchase #7 $220.29   13.852%   $250.8046   $250.80   $250.80   $250.80  
  7 purchase totals = $1,038.03       $1,148.1722   $1,148.17   $1,148.15   $1,148.20