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 $152.90   10.495%   $168.9469   $168.95   $168.95   $168.90  
  Purchase #2 $216.48   11.307%   $240.9574   $240.96   $240.95   $241.00  
  Purchase #3 $12.92   4.238%   $13.4675   $13.47   $13.45   $13.50  
  Purchase #4 $201.65   4.801%   $211.3312   $211.33   $211.35   $211.30  
  Purchase #5 $114.92   6.642%   $122.553   $122.55   $122.55   $122.60  
  Purchase #6 $206.97   5.837%   $219.0508   $219.05   $219.05   $219.10  
  Purchase #7 $214.45   3.377%   $221.692   $221.69   $221.70   $221.70  
  7 purchase totals = $1,120.29       $1,197.9988   $1,198.00   $1,198.00   $1,198.10