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 $95.30   11.533%   $106.2909   $106.29   $106.30   $106.30  
  Purchase #2 $176.32   8.466%   $191.2473   $191.25   $191.25   $191.20  
  Purchase #3 $147.25   4.547%   $153.9455   $153.95   $153.95   $153.90  
  Purchase #4 $177.90   13.454%   $201.8347   $201.83   $201.85   $201.80  
  Purchase #5 $158.92   10.187%   $175.1092   $175.11   $175.10   $175.10  
  Purchase #6 $46.50   7.796%   $50.1251   $50.13   $50.15   $50.10  
  Purchase #7 $160.96   10.694%   $178.1731   $178.17   $178.15   $178.20  
  7 purchase totals = $963.15       $1,056.7258   $1,056.73   $1,056.75   $1,056.60