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 $87.68   7.232%   $94.021   $94.02   $94.00   $94.00  
  Purchase #2 $59.47   9.659%   $65.2142   $65.21   $65.20   $65.20  
  Purchase #3 $196.37   11.340%   $218.6384   $218.64   $218.65   $218.60  
  Purchase #4 $214.28   4.681%   $224.3104   $224.31   $224.30   $224.30  
  Purchase #5 $204.81   3.231%   $211.4274   $211.43   $211.45   $211.40  
  Purchase #6 $159.29   3.575%   $164.9846   $164.98   $165.00   $165.00  
  Purchase #7 $247.89   12.382%   $278.5837   $278.58   $278.60   $278.60  
  7 purchase totals = $1,169.79       $1,257.1797   $1,257.17   $1,257.20   $1,257.10