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 $96.58   5.523%   $101.9141   $101.91   $101.90   $101.90  
  Purchase #2 $31.79   8.732%   $34.5659   $34.57   $34.55   $34.60  
  Purchase #3 $178.65   13.132%   $202.1103   $202.11   $202.10   $202.10  
  Purchase #4 $22.52   13.313%   $25.5181   $25.52   $25.50   $25.50  
  Purchase #5 $241.99   4.555%   $253.0126   $253.01   $253.00   $253.00  
  Purchase #6 $61.90   5.468%   $65.2847   $65.28   $65.30   $65.30  
  Purchase #7 $249.89   3.726%   $259.2009   $259.20   $259.20   $259.20  
  7 purchase totals = $883.32       $941.6066   $941.60   $941.55   $941.60