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 $13.67   3.732%   $14.1802   $14.18   $14.20   $14.20  
  Purchase #2 $212.78   9.104%   $232.1515   $232.15   $232.15   $232.20  
  Purchase #3 $191.31   3.817%   $198.6123   $198.61   $198.60   $198.60  
  Purchase #4 $211.27   4.345%   $220.4497   $220.45   $220.45   $220.40  
  Purchase #5 $203.46   7.864%   $219.4601   $219.46   $219.45   $219.50  
  Purchase #6 $57.30   12.416%   $64.4144   $64.41   $64.40   $64.40  
  Purchase #7 $55.42   4.808%   $58.0846   $58.08   $58.10   $58.10  
  7 purchase totals = $945.21       $1,007.3528   $1,007.34   $1,007.35   $1,007.40