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 $58.96   3.462%   $61.0012   $61.00   $61.00   $61.00  
  Purchase #2 $69.60   4.864%   $72.9853   $72.99   $73.00   $73.00  
  Purchase #3 $40.59   6.510%   $43.2324   $43.23   $43.25   $43.20  
  Purchase #4 $191.34   8.618%   $207.8297   $207.83   $207.85   $207.80  
  Purchase #5 $142.25   9.685%   $156.0269   $156.03   $156.05   $156.00  
  Purchase #6 $82.51   5.241%   $86.8343   $86.83   $86.85   $86.80  
  Purchase #7 $85.45   6.820%   $91.2777   $91.28   $91.30   $91.30  
  7 purchase totals = $670.70       $719.1875   $719.19   $719.30   $719.10