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 $194.84   5.714%   $205.9732   $205.97   $205.95   $206.00  
  Purchase #2 $62.95   4.289%   $65.6499   $65.65   $65.65   $65.60  
  Purchase #3 $240.91   7.385%   $258.7012   $258.70   $258.70   $258.70  
  Purchase #4 $89.95   5.601%   $94.9881   $94.99   $95.00   $95.00  
  Purchase #5 $163.30   7.836%   $176.0962   $176.10   $176.10   $176.10  
  Purchase #6 $173.92   7.627%   $187.1849   $187.18   $187.20   $187.20  
  Purchase #7 $21.37   13.747%   $24.3077   $24.31   $24.30   $24.30  
  7 purchase totals = $947.24       $1,012.9012   $1,012.90   $1,012.90   $1,012.90