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 $43.41   8.530%   $47.1129   $47.11   $47.10   $47.10  
  Purchase #2 $97.66   7.372%   $104.8595   $104.86   $104.85   $104.90  
  Purchase #3 $165.43   9.833%   $181.6967   $181.70   $181.70   $181.70  
  Purchase #4 $248.39   12.610%   $279.712   $279.71   $279.70   $279.70  
  Purchase #5 $69.80   8.624%   $75.8196   $75.82   $75.80   $75.80  
  Purchase #6 $101.46   8.377%   $109.9593   $109.96   $109.95   $110.00  
  Purchase #7 $219.93   13.235%   $249.0377   $249.04   $249.05   $249.00  
  7 purchase totals = $946.08       $1,048.1977   $1,048.20   $1,048.15   $1,048.20