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 $244.48   7.420%   $262.6204   $262.62   $262.60   $262.60  
  Purchase #2 $71.80   3.447%   $74.2749   $74.27   $74.25   $74.30  
  Purchase #3 $156.80   11.802%   $175.3055   $175.31   $175.30   $175.30  
  Purchase #4 $85.41   13.662%   $97.0787   $97.08   $97.10   $97.10  
  Purchase #5 $180.63   12.676%   $203.5267   $203.53   $203.55   $203.50  
  Purchase #6 $213.83   6.702%   $228.1609   $228.16   $228.15   $228.20  
  Purchase #7 $14.46   3.842%   $15.0156   $15.02   $15.00   $15.00  
  7 purchase totals = $967.41       $1,055.9827   $1,055.99   $1,055.95   $1,056.00