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 $214.35   10.602%   $237.0754   $237.08   $237.10   $237.10  
  Purchase #2 $242.77   13.116%   $274.6117   $274.61   $274.60   $274.60  
  Purchase #3 $136.29   11.695%   $152.2291   $152.23   $152.25   $152.20  
  Purchase #4 $13.95   4.540%   $14.5833   $14.58   $14.60   $14.60  
  Purchase #5 $67.59   9.802%   $74.2152   $74.22   $74.20   $74.20  
  Purchase #6 $199.84   6.589%   $213.0075   $213.01   $213.00   $213.00  
  Purchase #7 $138.82   8.511%   $150.635   $150.64   $150.65   $150.60  
  7 purchase totals = $1,013.61       $1,116.3572   $1,116.37   $1,116.40   $1,116.30