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 $214.98   6.361%   $228.6549   $228.65   $228.65   $228.70  
  Purchase #2 $191.95   13.379%   $217.631   $217.63   $217.65   $217.60  
  Purchase #3 $44.50   10.218%   $49.047   $49.05   $49.05   $49.00  
  Purchase #4 $166.58   7.576%   $179.2001   $179.20   $179.20   $179.20  
  Purchase #5 $165.52   9.564%   $181.3503   $181.35   $181.35   $181.40  
  Purchase #6 $106.76   11.151%   $118.6648   $118.66   $118.65   $118.70  
  Purchase #7 $32.40   4.810%   $33.9584   $33.96   $33.95   $34.00  
  7 purchase totals = $922.69       $1,008.5065   $1,008.50   $1,008.50   $1,008.60