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 $169.36   7.471%   $182.0129   $182.01   $182.00   $182.00  
  Purchase #2 $203.71   13.179%   $230.5569   $230.56   $230.55   $230.60  
  Purchase #3 $44.64   11.479%   $49.7642   $49.76   $49.75   $49.80  
  Purchase #4 $218.82   13.178%   $247.6561   $247.66   $247.65   $247.70  
  Purchase #5 $52.83   6.731%   $56.386   $56.39   $56.40   $56.40  
  Purchase #6 $138.44   6.466%   $147.3915   $147.39   $147.40   $147.40  
  Purchase #7 $139.88   3.844%   $145.257   $145.26   $145.25   $145.30  
  7 purchase totals = $967.68       $1,059.0246   $1,059.03   $1,059.00   $1,059.20