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 $118.65   6.773%   $126.6862   $126.69   $126.70   $126.70  
  Purchase #2 $193.82   10.230%   $213.6478   $213.65   $213.65   $213.60  
  Purchase #3 $83.90   11.415%   $93.4772   $93.48   $93.50   $93.50  
  Purchase #4 $229.65   5.816%   $243.0064   $243.01   $243.00   $243.00  
  Purchase #5 $180.69   13.484%   $205.0542   $205.05   $205.05   $205.10  
  Purchase #6 $165.94   12.131%   $186.0702   $186.07   $186.05   $186.10  
  Purchase #7 $104.62   6.581%   $111.505   $111.51   $111.50   $111.50  
  7 purchase totals = $1,077.27       $1,179.4470   $1,179.46   $1,179.45   $1,179.50