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 $167.51   11.778%   $187.2393   $187.24   $187.25   $187.20  
  Purchase #2 $101.91   13.448%   $115.6149   $115.61   $115.60   $115.60  
  Purchase #3 $204.52   11.677%   $228.4018   $228.40   $228.40   $228.40  
  Purchase #4 $191.65   6.210%   $203.5515   $203.55   $203.55   $203.60  
  Purchase #5 $53.60   8.667%   $58.2455   $58.25   $58.25   $58.20  
  Purchase #6 $134.35   4.658%   $140.608   $140.61   $140.60   $140.60  
  Purchase #7 $245.70   6.368%   $261.3462   $261.35   $261.35   $261.30  
  7 purchase totals = $1,099.24       $1,195.0072   $1,195.01   $1,195.00   $1,194.90