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 $92.42   3.611%   $95.7573   $95.76   $95.75   $95.80  
  Purchase #2 $41.34   12.638%   $46.5645   $46.56   $46.55   $46.60  
  Purchase #3 $204.80   4.217%   $213.4364   $213.44   $213.45   $213.40  
  Purchase #4 $235.99   4.808%   $247.3364   $247.34   $247.35   $247.30  
  Purchase #5 $166.82   11.658%   $186.2679   $186.27   $186.25   $186.30  
  Purchase #6 $187.49   6.862%   $200.3556   $200.36   $200.35   $200.40  
  Purchase #7 $159.74   10.823%   $177.0287   $177.03   $177.05   $177.00  
  7 purchase totals = $1,088.60       $1,166.7468   $1,166.76   $1,166.75   $1,166.80