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 $125.69   6.563%   $133.939   $133.94   $133.95   $133.90  
  Purchase #2 $106.54   4.819%   $111.6742   $111.67   $111.65   $111.70  
  Purchase #3 $229.67   6.243%   $244.0083   $244.01   $244.00   $244.00  
  Purchase #4 $177.84   6.722%   $189.7944   $189.79   $189.80   $189.80  
  Purchase #5 $205.44   6.699%   $219.2024   $219.20   $219.20   $219.20  
  Purchase #6 $78.95   5.204%   $83.0586   $83.06   $83.05   $83.10  
  Purchase #7 $27.44   6.706%   $29.2801   $29.28   $29.30   $29.30  
  7 purchase totals = $951.57       $1,010.9570   $1,010.95   $1,010.95   $1,011.00