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 $177.36   11.397%   $197.5737   $197.57   $197.55   $197.60  
  Purchase #2 $95.52   7.105%   $102.3067   $102.31   $102.30   $102.30  
  Purchase #3 $94.52   11.678%   $105.558   $105.56   $105.55   $105.60  
  Purchase #4 $22.70   6.546%   $24.1859   $24.19   $24.20   $24.20  
  Purchase #5 $176.61   8.694%   $191.9645   $191.96   $191.95   $192.00  
  Purchase #6 $172.76   5.320%   $181.9508   $181.95   $181.95   $182.00  
  Purchase #7 $217.70   11.349%   $242.4068   $242.41   $242.40   $242.40  
  7 purchase totals = $957.17       $1,045.9464   $1,045.95   $1,045.90   $1,046.10