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 $109.97   5.526%   $116.0469   $116.05   $116.05   $116.00  
  Purchase #2 $37.84   9.332%   $41.3712   $41.37   $41.35   $41.40  
  Purchase #3 $95.71   7.456%   $102.8461   $102.85   $102.85   $102.80  
  Purchase #4 $147.53   8.723%   $160.399   $160.40   $160.40   $160.40  
  Purchase #5 $197.36   4.607%   $206.4524   $206.45   $206.45   $206.50  
  Purchase #6 $238.40   6.688%   $254.3442   $254.34   $254.35   $254.30  
  Purchase #7 $167.88   11.705%   $187.5304   $187.53   $187.55   $187.50  
  7 purchase totals = $994.69       $1,068.9902   $1,068.99   $1,069.00   $1,068.90