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 $194.50   12.698%   $219.1976   $219.20   $219.20   $219.20  
  Purchase #2 $232.80   12.713%   $262.3959   $262.40   $262.40   $262.40  
  Purchase #3 $165.57   3.605%   $171.5388   $171.54   $171.55   $171.50  
  Purchase #4 $104.35   11.698%   $116.5569   $116.56   $116.55   $116.60  
  Purchase #5 $35.72   11.344%   $39.7721   $39.77   $39.75   $39.80  
  Purchase #6 $105.91   4.822%   $111.017   $111.02   $111.00   $111.00  
  Purchase #7 $180.74   9.777%   $198.4109   $198.41   $198.40   $198.40  
  7 purchase totals = $1,019.59       $1,118.8892   $1,118.90   $1,118.85   $1,118.90