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 $53.88   13.402%   $61.101   $61.10   $61.10   $61.10  
  Purchase #2 $183.92   11.562%   $205.1848   $205.18   $205.20   $205.20  
  Purchase #3 $170.48   9.839%   $187.2535   $187.25   $187.25   $187.30  
  Purchase #4 $239.40   6.160%   $254.147   $254.15   $254.15   $254.10  
  Purchase #5 $124.47   13.735%   $141.566   $141.57   $141.55   $141.60  
  Purchase #6 $70.28   5.595%   $74.2122   $74.21   $74.20   $74.20  
  Purchase #7 $203.91   9.465%   $223.2101   $223.21   $223.20   $223.20  
  7 purchase totals = $1,046.34       $1,146.6746   $1,146.67   $1,146.65   $1,146.70