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 $58.51   9.313%   $63.959   $63.96   $63.95   $64.00  
  Purchase #2 $108.58   6.632%   $115.781   $115.78   $115.80   $115.80  
  Purchase #3 $38.80   6.461%   $41.3069   $41.31   $41.30   $41.30  
  Purchase #4 $32.83   8.600%   $35.6534   $35.65   $35.65   $35.70  
  Purchase #5 $231.65   8.781%   $251.9912   $251.99   $252.00   $252.00  
  Purchase #6 $131.31   4.667%   $137.4382   $137.44   $137.45   $137.40  
  Purchase #7 $96.30   13.478%   $109.2793   $109.28   $109.30   $109.30  
  7 purchase totals = $697.98       $755.4090   $755.41   $755.45   $755.50