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 $179.61   8.755%   $195.3349   $195.33   $195.35   $195.30  
  Purchase #2 $174.70   13.144%   $197.6626   $197.66   $197.65   $197.70  
  Purchase #3 $193.28   6.396%   $205.6422   $205.64   $205.65   $205.60  
  Purchase #4 $179.79   13.734%   $204.4824   $204.48   $204.50   $204.50  
  Purchase #5 $149.65   4.149%   $155.859   $155.86   $155.85   $155.90  
  Purchase #6 $218.60   6.204%   $232.1619   $232.16   $232.15   $232.20  
  Purchase #7 $209.82   7.713%   $226.0034   $226.00   $226.00   $226.00  
  7 purchase totals = $1,305.45       $1,417.1464   $1,417.13   $1,417.15   $1,417.20