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 $214.68   9.719%   $235.5447   $235.54   $235.55   $235.50  
  Purchase #2 $69.44   5.610%   $73.3356   $73.34   $73.35   $73.30  
  Purchase #3 $30.77   9.660%   $33.7424   $33.74   $33.75   $33.70  
  Purchase #4 $214.49   13.428%   $243.2917   $243.29   $243.30   $243.30  
  Purchase #5 $40.58   11.492%   $45.2435   $45.24   $45.25   $45.20  
  Purchase #6 $209.64   6.543%   $223.3567   $223.36   $223.35   $223.40  
  Purchase #7 $226.53   6.619%   $241.524   $241.52   $241.50   $241.50  
  7 purchase totals = $1,006.13       $1,096.0386   $1,096.03   $1,096.05   $1,095.90