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 $191.98   13.229%   $217.377   $217.38   $217.40   $217.40  
  Purchase #2 $217.42   7.675%   $234.107   $234.11   $234.10   $234.10  
  Purchase #3 $187.84   3.748%   $194.8802   $194.88   $194.90   $194.90  
  Purchase #4 $179.40   6.317%   $190.7327   $190.73   $190.75   $190.70  
  Purchase #5 $107.26   7.270%   $115.0578   $115.06   $115.05   $115.10  
  Purchase #6 $51.64   7.191%   $55.3534   $55.35   $55.35   $55.40  
  Purchase #7 $180.52   7.187%   $193.494   $193.49   $193.50   $193.50  
  7 purchase totals = $1,116.06       $1,201.0021   $1,201.00   $1,201.05   $1,201.10