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 $158.51   11.365%   $176.5247   $176.52   $176.50   $176.50  
  Purchase #2 $102.82   13.445%   $116.6441   $116.64   $116.65   $116.60  
  Purchase #3 $98.52   12.637%   $110.97   $110.97   $110.95   $111.00  
  Purchase #4 $165.56   6.475%   $176.28   $176.28   $176.30   $176.30  
  Purchase #5 $70.87   5.679%   $74.8947   $74.89   $74.90   $74.90  
  Purchase #6 $179.57   12.740%   $202.4472   $202.45   $202.45   $202.40  
  Purchase #7 $232.94   7.135%   $249.5603   $249.56   $249.55   $249.60  
  7 purchase totals = $1,008.79       $1,107.3210   $1,107.31   $1,107.30   $1,107.30