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 $58.83   7.654%   $63.3328   $63.33   $63.35   $63.30  
  Purchase #2 $219.58   4.173%   $228.7431   $228.74   $228.75   $228.70  
  Purchase #3 $197.74   3.438%   $204.5383   $204.54   $204.55   $204.50  
  Purchase #4 $146.97   12.328%   $165.0885   $165.09   $165.10   $165.10  
  Purchase #5 $181.25   12.522%   $203.9461   $203.95   $203.95   $203.90  
  Purchase #6 $185.33   5.656%   $195.8123   $195.81   $195.80   $195.80  
  Purchase #7 $156.57   4.514%   $163.6376   $163.64   $163.65   $163.60  
  7 purchase totals = $1,146.27       $1,225.0987   $1,225.10   $1,225.15   $1,224.90