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 $198.68   6.308%   $211.2127   $211.21   $211.20   $211.20  
  Purchase #2 $110.71   7.186%   $118.6656   $118.67   $118.65   $118.70  
  Purchase #3 $180.56   13.279%   $204.5366   $204.54   $204.55   $204.50  
  Purchase #4 $198.99   5.106%   $209.1504   $209.15   $209.15   $209.20  
  Purchase #5 $242.73   8.395%   $263.1072   $263.11   $263.10   $263.10  
  Purchase #6 $193.67   10.506%   $214.017   $214.02   $214.00   $214.00  
  Purchase #7 $170.56   6.481%   $181.614   $181.61   $181.60   $181.60  
  7 purchase totals = $1,295.90       $1,402.3035   $1,402.31   $1,402.25   $1,402.30