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 $183.99   7.232%   $197.2962   $197.30   $197.30   $197.30  
  Purchase #2 $209.74   8.220%   $226.9806   $226.98   $227.00   $227.00  
  Purchase #3 $219.30   6.614%   $233.8045   $233.80   $233.80   $233.80  
  Purchase #4 $24.29   7.659%   $26.1504   $26.15   $26.15   $26.20  
  Purchase #5 $105.75   5.124%   $111.1686   $111.17   $111.15   $111.20  
  Purchase #6 $83.57   11.539%   $93.2131   $93.21   $93.20   $93.20  
  Purchase #7 $200.61   10.528%   $221.7302   $221.73   $221.75   $221.70  
  7 purchase totals = $1,027.25       $1,110.3436   $1,110.34   $1,110.35   $1,110.40