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 $171.84   13.137%   $194.4146   $194.41   $194.40   $194.40  
  Purchase #2 $187.51   13.250%   $212.3551   $212.36   $212.35   $212.40  
  Purchase #3 $38.88   5.446%   $40.9974   $41.00   $41.00   $41.00  
  Purchase #4 $167.35   5.624%   $176.7618   $176.76   $176.75   $176.80  
  Purchase #5 $198.73   5.179%   $209.0222   $209.02   $209.00   $209.00  
  Purchase #6 $190.59   5.267%   $200.6284   $200.63   $200.65   $200.60  
  Purchase #7 $170.74   6.703%   $182.1847   $182.18   $182.20   $182.20  
  7 purchase totals = $1,125.64       $1,216.3642   $1,216.36   $1,216.35   $1,216.40