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 $192.95   11.484%   $215.1084   $215.11   $215.10   $215.10  
  Purchase #2 $238.92   5.193%   $251.3271   $251.33   $251.35   $251.30  
  Purchase #3 $8.69   12.243%   $9.7539   $9.75   $9.75   $9.80  
  Purchase #4 $156.57   13.496%   $177.7007   $177.70   $177.70   $177.70  
  Purchase #5 $185.83   3.607%   $192.5329   $192.53   $192.55   $192.50  
  Purchase #6 $202.31   5.239%   $212.909   $212.91   $212.90   $212.90  
  Purchase #7 $67.85   7.584%   $72.9957   $73.00   $73.00   $73.00  
  7 purchase totals = $1,053.12       $1,132.3277   $1,132.33   $1,132.35   $1,132.30