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 $91.76   4.393%   $95.791   $95.79   $95.80   $95.80  
  Purchase #2 $156.28   9.655%   $171.3688   $171.37   $171.35   $171.40  
  Purchase #3 $221.89   9.856%   $243.7595   $243.76   $243.75   $243.80  
  Purchase #4 $247.70   4.593%   $259.0769   $259.08   $259.10   $259.10  
  Purchase #5 $87.73   3.295%   $90.6207   $90.62   $90.60   $90.60  
  Purchase #6 $219.60   11.590%   $245.0516   $245.05   $245.05   $245.10  
  Purchase #7 $210.51   13.182%   $238.2594   $238.26   $238.25   $238.30  
  7 purchase totals = $1,235.47       $1,343.9279   $1,343.93   $1,343.90   $1,344.10