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 $41.29   5.793%   $43.6819   $43.68   $43.70   $43.70  
  Purchase #2 $169.33   13.705%   $192.5367   $192.54   $192.55   $192.50  
  Purchase #3 $187.75   11.338%   $209.0371   $209.04   $209.05   $209.00  
  Purchase #4 $77.80   8.201%   $84.1804   $84.18   $84.20   $84.20  
  Purchase #5 $120.52   4.326%   $125.7337   $125.73   $125.75   $125.70  
  Purchase #6 $94.53   12.211%   $106.0731   $106.07   $106.05   $106.10  
  Purchase #7 $9.87   12.587%   $11.1123   $11.11   $11.10   $11.10  
  7 purchase totals = $701.09       $772.3552   $772.35   $772.40   $772.30