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 $191.39   10.743%   $211.951   $211.95   $211.95   $212.00  
  Purchase #2 $98.59   7.577%   $106.0602   $106.06   $106.05   $106.10  
  Purchase #3 $52.83   10.142%   $58.188   $58.19   $58.20   $58.20  
  Purchase #4 $248.29   12.306%   $278.8446   $278.84   $278.85   $278.80  
  Purchase #5 $207.35   6.398%   $220.6163   $220.62   $220.60   $220.60  
  Purchase #6 $101.82   13.578%   $115.6451   $115.65   $115.65   $115.60  
  Purchase #7 $152.73   9.595%   $167.3844   $167.38   $167.40   $167.40  
  7 purchase totals = $1,053.00       $1,158.6896   $1,158.69   $1,158.70   $1,158.70