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 $194.37   4.818%   $203.7347   $203.73   $203.75   $203.70  
  Purchase #2 $185.58   13.238%   $210.1471   $210.15   $210.15   $210.10  
  Purchase #3 $89.56   7.527%   $96.3012   $96.30   $96.30   $96.30  
  Purchase #4 $219.43   10.553%   $242.5864   $242.59   $242.60   $242.60  
  Purchase #5 $129.44   3.227%   $133.617   $133.62   $133.60   $133.60  
  Purchase #6 $161.62   3.608%   $167.4512   $167.45   $167.45   $167.50  
  Purchase #7 $7.98   3.580%   $8.2657   $8.27   $8.25   $8.30  
  7 purchase totals = $987.98       $1,062.1033   $1,062.11   $1,062.10   $1,062.10