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 $207.52   12.760%   $233.9996   $234.00   $234.00   $234.00  
  Purchase #2 $232.39   9.207%   $253.7861   $253.79   $253.80   $253.80  
  Purchase #3 $41.92   13.367%   $47.5234   $47.52   $47.50   $47.50  
  Purchase #4 $43.80   13.599%   $49.7564   $49.76   $49.75   $49.80  
  Purchase #5 $176.42   6.562%   $187.9967   $188.00   $188.00   $188.00  
  Purchase #6 $158.62   10.590%   $175.4179   $175.42   $175.40   $175.40  
  Purchase #7 $200.80   7.704%   $216.2696   $216.27   $216.25   $216.30  
  7 purchase totals = $1,061.47       $1,164.7497   $1,164.76   $1,164.70   $1,164.80