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 $95.56   11.634%   $106.6775   $106.68   $106.70   $106.70  
  Purchase #2 $159.55   13.859%   $181.662   $181.66   $181.65   $181.70  
  Purchase #3 $83.96   8.851%   $91.3913   $91.39   $91.40   $91.40  
  Purchase #4 $152.93   12.438%   $171.9514   $171.95   $171.95   $172.00  
  Purchase #5 $76.37   11.449%   $85.1136   $85.11   $85.10   $85.10  
  Purchase #6 $120.70   4.360%   $125.9625   $125.96   $125.95   $126.00  
  Purchase #7 $132.97   9.283%   $145.3136   $145.31   $145.30   $145.30  
  7 purchase totals = $822.04       $908.0719   $908.06   $908.05   $908.20