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 $200.29   11.360%   $223.0429   $223.04   $223.05   $223.00  
  Purchase #2 $22.60   6.227%   $24.0073   $24.01   $24.00   $24.00  
  Purchase #3 $162.70   13.328%   $184.3847   $184.38   $184.40   $184.40  
  Purchase #4 $87.45   4.251%   $91.1675   $91.17   $91.15   $91.20  
  Purchase #5 $220.40   12.804%   $248.62   $248.62   $248.60   $248.60  
  Purchase #6 $161.70   10.242%   $178.2613   $178.26   $178.25   $178.30  
  Purchase #7 $147.35   3.687%   $152.7828   $152.78   $152.80   $152.80  
  7 purchase totals = $1,002.49       $1,102.2665   $1,102.26   $1,102.25   $1,102.30