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 $184.29   9.220%   $201.2815   $201.28   $201.30   $201.30  
  Purchase #2 $155.69   10.433%   $171.9331   $171.93   $171.95   $171.90  
  Purchase #3 $226.91   7.522%   $243.9782   $243.98   $244.00   $244.00  
  Purchase #4 $182.51   11.239%   $203.0223   $203.02   $203.00   $203.00  
  Purchase #5 $67.48   8.148%   $72.9783   $72.98   $73.00   $73.00  
  Purchase #6 $184.67   5.781%   $195.3458   $195.35   $195.35   $195.30  
  Purchase #7 $121.46   13.509%   $137.868   $137.87   $137.85   $137.90  
  7 purchase totals = $1,123.01       $1,226.4072   $1,226.41   $1,226.45   $1,226.40