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 $132.67   10.559%   $146.6786   $146.68   $146.70   $146.70  
  Purchase #2 $90.39   5.449%   $95.3154   $95.32   $95.30   $95.30  
  Purchase #3 $186.70   7.668%   $201.0162   $201.02   $201.00   $201.00  
  Purchase #4 $46.62   11.495%   $51.979   $51.98   $52.00   $52.00  
  Purchase #5 $234.39   6.399%   $249.3886   $249.39   $249.40   $249.40  
  Purchase #6 $137.91   4.838%   $144.5821   $144.58   $144.60   $144.60  
  Purchase #7 $219.40   5.140%   $230.6772   $230.68   $230.70   $230.70  
  7 purchase totals = $1,048.08       $1,119.6371   $1,119.65   $1,119.70   $1,119.70