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 $167.53   10.801%   $185.6249   $185.62   $185.60   $185.60  
  Purchase #2 $175.87   11.831%   $196.6772   $196.68   $196.70   $196.70  
  Purchase #3 $134.52   3.190%   $138.8112   $138.81   $138.80   $138.80  
  Purchase #4 $112.53   4.234%   $117.2945   $117.29   $117.30   $117.30  
  Purchase #5 $44.56   3.205%   $45.9881   $45.99   $46.00   $46.00  
  Purchase #6 $189.97   11.647%   $212.0958   $212.10   $212.10   $212.10  
  Purchase #7 $113.97   11.831%   $127.4538   $127.45   $127.45   $127.50  
  7 purchase totals = $938.95       $1,023.9455   $1,023.94   $1,023.95   $1,024.00