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 $41.70   7.287%   $44.7387   $44.74   $44.75   $44.70  
  Purchase #2 $204.32   7.326%   $219.2885   $219.29   $219.30   $219.30  
  Purchase #3 $207.89   11.511%   $231.8202   $231.82   $231.80   $231.80  
  Purchase #4 $93.51   11.643%   $104.3974   $104.40   $104.40   $104.40  
  Purchase #5 $190.88   8.794%   $207.666   $207.67   $207.65   $207.70  
  Purchase #6 $189.61   12.580%   $213.4629   $213.46   $213.45   $213.50  
  Purchase #7 $5.28   5.799%   $5.5862   $5.59   $5.60   $5.60  
  7 purchase totals = $933.19       $1,026.9599   $1,026.97   $1,026.95   $1,027.00