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 $175.56   4.824%   $184.029   $184.03   $184.05   $184.00  
  Purchase #2 $75.81   13.652%   $86.1596   $86.16   $86.15   $86.20  
  Purchase #3 $39.45   8.458%   $42.7867   $42.79   $42.80   $42.80  
  Purchase #4 $139.72   13.198%   $158.1602   $158.16   $158.15   $158.20  
  Purchase #5 $23.29   7.691%   $25.0812   $25.08   $25.10   $25.10  
  Purchase #6 $153.79   8.626%   $167.0559   $167.06   $167.05   $167.10  
  Purchase #7 $217.84   6.373%   $231.7229   $231.72   $231.70   $231.70  
  7 purchase totals = $825.46       $894.9955   $895.00   $895.00   $895.10