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 $186.44   7.810%   $201.001   $201.00   $201.00   $201.00  
  Purchase #2 $59.37   7.286%   $63.6957   $63.70   $63.70   $63.70  
  Purchase #3 $45.43   9.345%   $49.6754   $49.68   $49.70   $49.70  
  Purchase #4 $248.85   12.468%   $279.8766   $279.88   $279.90   $279.90  
  Purchase #5 $206.93   4.769%   $216.7985   $216.80   $216.80   $216.80  
  Purchase #6 $97.93   12.424%   $110.0968   $110.10   $110.10   $110.10  
  Purchase #7 $179.80   3.308%   $185.7478   $185.75   $185.75   $185.70  
  7 purchase totals = $1,024.75       $1,106.8918   $1,106.91   $1,106.95   $1,106.90