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 $61.96   12.732%   $69.8487   $69.85   $69.85   $69.80  
  Purchase #2 $201.99   6.189%   $214.4912   $214.49   $214.50   $214.50  
  Purchase #3 $179.53   6.360%   $190.9481   $190.95   $190.95   $190.90  
  Purchase #4 $99.35   12.281%   $111.5512   $111.55   $111.55   $111.60  
  Purchase #5 $247.25   9.810%   $271.5052   $271.51   $271.50   $271.50  
  Purchase #6 $71.34   6.211%   $75.7709   $75.77   $75.75   $75.80  
  Purchase #7 $202.79   8.419%   $219.8629   $219.86   $219.85   $219.90  
  7 purchase totals = $1,064.21       $1,153.9782   $1,153.98   $1,153.95   $1,154.00