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 $216.96   13.804%   $246.9092   $246.91   $246.90   $246.90  
  Purchase #2 $31.88   5.582%   $33.6595   $33.66   $33.65   $33.70  
  Purchase #3 $211.71   4.686%   $221.6307   $221.63   $221.65   $221.60  
  Purchase #4 $148.31   11.451%   $165.293   $165.29   $165.30   $165.30  
  Purchase #5 $46.58   3.492%   $48.2066   $48.21   $48.20   $48.20  
  Purchase #6 $205.57   3.326%   $212.4073   $212.41   $212.40   $212.40  
  Purchase #7 $203.86   5.517%   $215.107   $215.11   $215.10   $215.10  
  7 purchase totals = $1,064.87       $1,143.2133   $1,143.22   $1,143.20   $1,143.20