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 $98.84   8.221%   $106.9656   $106.97   $106.95   $107.00  
  Purchase #2 $170.81   6.823%   $182.4644   $182.46   $182.45   $182.50  
  Purchase #3 $208.43   11.323%   $232.0305   $232.03   $232.05   $232.00  
  Purchase #4 $104.58   13.188%   $118.372   $118.37   $118.35   $118.40  
  Purchase #5 $124.60   8.275%   $134.9107   $134.91   $134.90   $134.90  
  Purchase #6 $104.53   13.114%   $118.2381   $118.24   $118.25   $118.20  
  Purchase #7 $167.83   8.385%   $181.9025   $181.90   $181.90   $181.90  
  7 purchase totals = $979.62       $1,074.8838   $1,074.88   $1,074.85   $1,074.90