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 $195.70   3.358%   $202.2716   $202.27   $202.25   $202.30  
  Purchase #2 $246.64   9.299%   $269.5751   $269.58   $269.60   $269.60  
  Purchase #3 $15.44   7.494%   $16.5971   $16.60   $16.60   $16.60  
  Purchase #4 $240.50   7.478%   $258.4846   $258.48   $258.50   $258.50  
  Purchase #5 $106.59   9.395%   $116.6041   $116.60   $116.60   $116.60  
  Purchase #6 $220.37   3.688%   $228.4972   $228.50   $228.50   $228.50  
  Purchase #7 $141.46   10.750%   $156.667   $156.67   $156.65   $156.70  
  7 purchase totals = $1,166.70       $1,248.6967   $1,248.70   $1,248.70   $1,248.80