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 $92.42   4.711%   $96.7739   $96.77   $96.75   $96.80  
  Purchase #2 $114.69   6.699%   $122.3731   $122.37   $122.35   $122.40  
  Purchase #3 $149.68   10.309%   $165.1105   $165.11   $165.10   $165.10  
  Purchase #4 $79.93   4.519%   $83.542   $83.54   $83.55   $83.50  
  Purchase #5 $180.31   11.357%   $200.7878   $200.79   $200.80   $200.80  
  Purchase #6 $50.85   8.705%   $55.2765   $55.28   $55.30   $55.30  
  Purchase #7 $153.67   5.500%   $162.1219   $162.12   $162.10   $162.10  
  7 purchase totals = $821.55       $885.9857   $885.98   $885.95   $886.00