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 $58.69   7.586%   $63.1422   $63.14   $63.15   $63.10  
  Purchase #2 $202.65   5.605%   $214.0085   $214.01   $214.00   $214.00  
  Purchase #3 $227.65   3.315%   $235.1966   $235.20   $235.20   $235.20  
  Purchase #4 $160.38   13.124%   $181.4283   $181.43   $181.45   $181.40  
  Purchase #5 $147.36   4.108%   $153.4135   $153.41   $153.40   $153.40  
  Purchase #6 $138.30   5.683%   $146.1596   $146.16   $146.15   $146.20  
  Purchase #7 $26.62   11.755%   $29.7492   $29.75   $29.75   $29.70  
  7 purchase totals = $961.65       $1,023.0979   $1,023.10   $1,023.10   $1,023.00