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 $59.67   12.363%   $67.047   $67.05   $67.05   $67.00  
  Purchase #2 $37.39   3.140%   $38.564   $38.56   $38.55   $38.60  
  Purchase #3 $142.77   5.615%   $150.7865   $150.79   $150.80   $150.80  
  Purchase #4 $192.76   7.430%   $207.0821   $207.08   $207.10   $207.10  
  Purchase #5 $245.46   7.298%   $263.3737   $263.37   $263.35   $263.40  
  Purchase #6 $149.88   8.403%   $162.4744   $162.47   $162.45   $162.50  
  Purchase #7 $144.94   9.533%   $158.7571   $158.76   $158.75   $158.80  
  7 purchase totals = $972.87       $1,048.0848   $1,048.08   $1,048.05   $1,048.20