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 $84.28   12.677%   $94.9642   $94.96   $94.95   $95.00  
  Purchase #2 $196.84   7.493%   $211.5892   $211.59   $211.60   $211.60  
  Purchase #3 $23.92   11.276%   $26.6172   $26.62   $26.60   $26.60  
  Purchase #4 $208.78   11.241%   $232.249   $232.25   $232.25   $232.20  
  Purchase #5 $220.59   5.496%   $232.7136   $232.71   $232.70   $232.70  
  Purchase #6 $185.39   7.658%   $199.5872   $199.59   $199.60   $199.60  
  Purchase #7 $195.90   7.255%   $210.1125   $210.11   $210.10   $210.10  
  7 purchase totals = $1,115.70       $1,207.8329   $1,207.83   $1,207.80   $1,207.80