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 $177.54   7.560%   $190.962   $190.96   $190.95   $191.00  
  Purchase #2 $233.57   7.322%   $250.672   $250.67   $250.65   $250.70  
  Purchase #3 $181.67   5.427%   $191.5292   $191.53   $191.55   $191.50  
  Purchase #4 $166.74   4.688%   $174.5568   $174.56   $174.55   $174.60  
  Purchase #5 $46.53   12.151%   $52.1839   $52.18   $52.20   $52.20  
  Purchase #6 $26.32   11.469%   $29.3386   $29.34   $29.35   $29.30  
  Purchase #7 $232.68   11.751%   $260.0222   $260.02   $260.00   $260.00  
  7 purchase totals = $1,065.05       $1,149.2647   $1,149.26   $1,149.25   $1,149.30