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 $84.48   12.534%   $95.0687   $95.07   $95.05   $95.10  
  Purchase #2 $96.51   12.277%   $108.3585   $108.36   $108.35   $108.40  
  Purchase #3 $168.56   7.683%   $181.5105   $181.51   $181.50   $181.50  
  Purchase #4 $86.69   9.563%   $94.9802   $94.98   $95.00   $95.00  
  Purchase #5 $244.50   10.305%   $269.6957   $269.70   $269.70   $269.70  
  Purchase #6 $232.42   8.137%   $251.332   $251.33   $251.35   $251.30  
  Purchase #7 $81.64   6.478%   $86.9286   $86.93   $86.95   $86.90  
  7 purchase totals = $994.80       $1,087.8742   $1,087.88   $1,087.90   $1,087.90