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 $184.56   5.633%   $194.9563   $194.96   $194.95   $195.00  
  Purchase #2 $81.57   6.835%   $87.1453   $87.15   $87.15   $87.10  
  Purchase #3 $150.84   7.535%   $162.2058   $162.21   $162.20   $162.20  
  Purchase #4 $142.90   13.282%   $161.88   $161.88   $161.90   $161.90  
  Purchase #5 $200.30   9.721%   $219.7712   $219.77   $219.75   $219.80  
  Purchase #6 $123.67   13.589%   $140.4755   $140.48   $140.50   $140.50  
  Purchase #7 $166.71   12.474%   $187.5054   $187.51   $187.50   $187.50  
  7 purchase totals = $1,050.55       $1,153.9395   $1,153.96   $1,153.95   $1,154.00