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 $60.95   3.771%   $63.2484   $63.25   $63.25   $63.20  
  Purchase #2 $200.53   11.245%   $223.0796   $223.08   $223.10   $223.10  
  Purchase #3 $34.73   8.312%   $37.6168   $37.62   $37.60   $37.60  
  Purchase #4 $165.78   5.118%   $174.2646   $174.26   $174.25   $174.30  
  Purchase #5 $26.89   4.293%   $28.0444   $28.04   $28.05   $28.00  
  Purchase #6 $77.78   13.303%   $88.1271   $88.13   $88.15   $88.10  
  Purchase #7 $232.86   3.722%   $241.527   $241.53   $241.55   $241.50  
  7 purchase totals = $799.52       $855.9079   $855.91   $855.95   $855.80