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 $62.57   7.149%   $67.0431   $67.04   $67.05   $67.00  
  Purchase #2 $180.39   3.328%   $186.3934   $186.39   $186.40   $186.40  
  Purchase #3 $234.68   12.486%   $263.9821   $263.98   $264.00   $264.00  
  Purchase #4 $243.97   4.733%   $255.5171   $255.52   $255.50   $255.50  
  Purchase #5 $184.95   11.383%   $206.0029   $206.00   $206.00   $206.00  
  Purchase #6 $115.37   10.544%   $127.5346   $127.53   $127.55   $127.50  
  Purchase #7 $203.56   6.131%   $216.0403   $216.04   $216.05   $216.00  
  7 purchase totals = $1,225.49       $1,322.5135   $1,322.50   $1,322.55   $1,322.40