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 $43.40   7.401%   $46.612   $46.61   $46.60   $46.60  
  Purchase #2 $165.46   6.530%   $176.2645   $176.26   $176.25   $176.30  
  Purchase #3 $77.44   12.594%   $87.1928   $87.19   $87.20   $87.20  
  Purchase #4 $240.48   11.391%   $267.8731   $267.87   $267.85   $267.90  
  Purchase #5 $178.65   6.269%   $189.8496   $189.85   $189.85   $189.80  
  Purchase #6 $96.43   10.184%   $106.2504   $106.25   $106.25   $106.30  
  Purchase #7 $124.96   5.151%   $131.3967   $131.40   $131.40   $131.40  
  7 purchase totals = $926.82       $1,005.4391   $1,005.43   $1,005.40   $1,005.50