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 $193.93   3.866%   $201.4273   $201.43   $201.45   $201.40  
  Purchase #2 $84.47   13.459%   $95.8388   $95.84   $95.85   $95.80  
  Purchase #3 $187.34   3.272%   $193.4698   $193.47   $193.45   $193.50  
  Purchase #4 $106.34   3.163%   $109.7035   $109.70   $109.70   $109.70  
  Purchase #5 $87.44   6.604%   $93.2145   $93.21   $93.20   $93.20  
  Purchase #6 $173.45   4.423%   $181.1217   $181.12   $181.10   $181.10  
  Purchase #7 $152.80   3.495%   $158.1404   $158.14   $158.15   $158.10  
  7 purchase totals = $985.77       $1,032.9160   $1,032.91   $1,032.90   $1,032.80