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 $176.85   4.462%   $184.741   $184.74   $184.75   $184.70  
  Purchase #2 $178.54   9.817%   $196.0673   $196.07   $196.05   $196.10  
  Purchase #3 $75.87   13.293%   $85.9554   $85.96   $85.95   $86.00  
  Purchase #4 $136.67   10.487%   $151.0026   $151.00   $151.00   $151.00  
  Purchase #5 $186.70   3.695%   $193.5986   $193.60   $193.60   $193.60  
  Purchase #6 $245.34   10.586%   $271.3117   $271.31   $271.30   $271.30  
  Purchase #7 $102.64   6.632%   $109.4471   $109.45   $109.45   $109.40  
  7 purchase totals = $1,102.61       $1,192.1237   $1,192.13   $1,192.10   $1,192.10