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 $181.52   8.103%   $196.2286   $196.23   $196.25   $196.20  
  Purchase #2 $166.66   10.384%   $183.966   $183.97   $183.95   $184.00  
  Purchase #3 $28.69   11.565%   $32.008   $32.01   $32.00   $32.00  
  Purchase #4 $27.85   9.489%   $30.4927   $30.49   $30.50   $30.50  
  Purchase #5 $8.52   5.681%   $9.004   $9.00   $9.00   $9.00  
  Purchase #6 $219.50   6.343%   $233.4229   $233.42   $233.40   $233.40  
  Purchase #7 $77.70   6.249%   $82.5555   $82.56   $82.55   $82.60  
  7 purchase totals = $710.44       $767.6777   $767.68   $767.65   $767.70