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 $185.93   5.578%   $196.3012   $196.30   $196.30   $196.30  
  Purchase #2 $96.99   6.848%   $103.6319   $103.63   $103.65   $103.60  
  Purchase #3 $126.59   12.182%   $142.0112   $142.01   $142.00   $142.00  
  Purchase #4 $170.68   6.811%   $182.305   $182.31   $182.30   $182.30  
  Purchase #5 $93.37   8.252%   $101.0749   $101.07   $101.05   $101.10  
  Purchase #6 $108.95   13.792%   $123.9764   $123.98   $124.00   $124.00  
  Purchase #7 $190.69   6.359%   $202.816   $202.82   $202.80   $202.80  
  7 purchase totals = $973.20       $1,052.1166   $1,052.12   $1,052.10   $1,052.10