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 $193.46   7.693%   $208.3429   $208.34   $208.35   $208.30  
  Purchase #2 $212.82   12.649%   $239.7396   $239.74   $239.75   $239.70  
  Purchase #3 $218.60   5.225%   $230.0219   $230.02   $230.00   $230.00  
  Purchase #4 $95.26   12.407%   $107.0789   $107.08   $107.10   $107.10  
  Purchase #5 $204.74   7.450%   $219.9931   $219.99   $220.00   $220.00  
  Purchase #6 $53.60   3.862%   $55.67   $55.67   $55.65   $55.70  
  Purchase #7 $247.69   11.173%   $275.3644   $275.36   $275.35   $275.40  
  7 purchase totals = $1,226.17       $1,336.2108   $1,336.20   $1,336.20   $1,336.20