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 $184.75   5.482%   $194.878   $194.88   $194.90   $194.90  
  Purchase #2 $111.41   7.513%   $119.7802   $119.78   $119.80   $119.80  
  Purchase #3 $57.70   4.440%   $60.2619   $60.26   $60.25   $60.30  
  Purchase #4 $78.45   13.115%   $88.7387   $88.74   $88.75   $88.70  
  Purchase #5 $196.80   10.809%   $218.0721   $218.07   $218.05   $218.10  
  Purchase #6 $216.37   12.327%   $243.0419   $243.04   $243.05   $243.00  
  Purchase #7 $230.64   4.636%   $241.3325   $241.33   $241.35   $241.30  
  7 purchase totals = $1,076.12       $1,166.1053   $1,166.10   $1,166.15   $1,166.10