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 $152.78   7.307%   $163.9436   $163.94   $163.95   $163.90  
  Purchase #2 $206.68   11.445%   $230.3345   $230.33   $230.35   $230.30  
  Purchase #3 $70.68   10.724%   $78.2597   $78.26   $78.25   $78.30  
  Purchase #4 $82.43   12.796%   $92.9777   $92.98   $93.00   $93.00  
  Purchase #5 $147.84   5.453%   $155.9017   $155.90   $155.90   $155.90  
  Purchase #6 $228.70   11.519%   $255.044   $255.04   $255.05   $255.00  
  Purchase #7 $119.62   6.347%   $127.2123   $127.21   $127.20   $127.20  
  7 purchase totals = $1,008.73       $1,103.6735   $1,103.66   $1,103.70   $1,103.60