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 $184.50   9.671%   $202.343   $202.34   $202.35   $202.30  
  Purchase #2 $249.38   11.631%   $278.3854   $278.39   $278.40   $278.40  
  Purchase #3 $179.34   12.671%   $202.0642   $202.06   $202.05   $202.10  
  Purchase #4 $77.99   10.103%   $85.8693   $85.87   $85.85   $85.90  
  Purchase #5 $191.96   7.650%   $206.6449   $206.64   $206.65   $206.60  
  Purchase #6 $73.34   13.113%   $82.9571   $82.96   $82.95   $83.00  
  Purchase #7 $151.52   11.283%   $168.616   $168.62   $168.60   $168.60  
  7 purchase totals = $1,108.03       $1,226.8799   $1,226.88   $1,226.85   $1,226.90