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 $179.36   8.523%   $194.6469   $194.65   $194.65   $194.60  
  Purchase #2 $128.50   8.124%   $138.9393   $138.94   $138.95   $138.90  
  Purchase #3 $59.62   7.391%   $64.0265   $64.03   $64.05   $64.00  
  Purchase #4 $239.55   8.283%   $259.3919   $259.39   $259.40   $259.40  
  Purchase #5 $93.93   3.241%   $96.9743   $96.97   $96.95   $97.00  
  Purchase #6 $205.73   4.549%   $215.0887   $215.09   $215.10   $215.10  
  Purchase #7 $98.84   9.799%   $108.5253   $108.53   $108.55   $108.50  
  7 purchase totals = $1,005.53       $1,077.5929   $1,077.60   $1,077.65   $1,077.50