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 $112.60   6.195%   $119.5756   $119.58   $119.60   $119.60  
  Purchase #2 $96.60   8.350%   $104.6661   $104.67   $104.65   $104.70  
  Purchase #3 $177.84   9.159%   $194.1284   $194.13   $194.15   $194.10  
  Purchase #4 $199.92   11.683%   $223.2767   $223.28   $223.30   $223.30  
  Purchase #5 $125.64   12.337%   $141.1402   $141.14   $141.15   $141.10  
  Purchase #6 $66.87   11.299%   $74.4256   $74.43   $74.45   $74.40  
  Purchase #7 $194.72   3.852%   $202.2206   $202.22   $202.20   $202.20  
  7 purchase totals = $974.19       $1,059.4332   $1,059.45   $1,059.50   $1,059.40