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 $69.26   7.520%   $74.4684   $74.47   $74.45   $74.50  
  Purchase #2 $127.67   10.482%   $141.0524   $141.05   $141.05   $141.10  
  Purchase #3 $147.79   13.340%   $167.5052   $167.51   $167.50   $167.50  
  Purchase #4 $229.94   9.721%   $252.2925   $252.29   $252.30   $252.30  
  Purchase #5 $206.49   11.774%   $230.8021   $230.80   $230.80   $230.80  
  Purchase #6 $131.31   4.102%   $136.6963   $136.70   $136.70   $136.70  
  Purchase #7 $20.32   3.249%   $20.9802   $20.98   $21.00   $21.00  
  7 purchase totals = $932.78       $1,023.7971   $1,023.80   $1,023.80   $1,023.90