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 $62.38   11.458%   $69.5275   $69.53   $69.55   $69.50  
  Purchase #2 $31.73   8.334%   $34.3744   $34.37   $34.35   $34.40  
  Purchase #3 $191.80   13.523%   $217.7371   $217.74   $217.75   $217.70  
  Purchase #4 $171.30   12.267%   $192.3134   $192.31   $192.30   $192.30  
  Purchase #5 $178.46   11.113%   $198.2923   $198.29   $198.30   $198.30  
  Purchase #6 $162.62   6.261%   $172.8016   $172.80   $172.80   $172.80  
  Purchase #7 $193.34   11.711%   $215.982   $215.98   $216.00   $216.00  
  7 purchase totals = $991.63       $1,101.0283   $1,101.02   $1,101.05   $1,101.00