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 $88.61   8.511%   $96.1516   $96.15   $96.15   $96.20  
  Purchase #2 $203.97   4.773%   $213.7055   $213.71   $213.70   $213.70  
  Purchase #3 $116.45   5.403%   $122.7418   $122.74   $122.75   $122.70  
  Purchase #4 $172.89   13.196%   $195.7046   $195.70   $195.70   $195.70  
  Purchase #5 $62.82   7.375%   $67.453   $67.45   $67.45   $67.50  
  Purchase #6 $219.53   9.362%   $240.0824   $240.08   $240.10   $240.10  
  Purchase #7 $153.64   5.500%   $162.0902   $162.09   $162.10   $162.10  
  7 purchase totals = $1,017.91       $1,097.9291   $1,097.92   $1,097.95   $1,098.00