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 $92.95   3.566%   $96.2646   $96.26   $96.25   $96.30  
  Purchase #2 $234.89   9.169%   $256.4271   $256.43   $256.45   $256.40  
  Purchase #3 $71.72   7.272%   $76.9355   $76.94   $76.95   $76.90  
  Purchase #4 $61.84   9.429%   $67.6709   $67.67   $67.65   $67.70  
  Purchase #5 $116.32   4.320%   $121.345   $121.35   $121.35   $121.30  
  Purchase #6 $235.53   8.862%   $256.4027   $256.40   $256.40   $256.40  
  Purchase #7 $165.80   4.684%   $173.5661   $173.57   $173.55   $173.60  
  7 purchase totals = $979.05       $1,048.6119   $1,048.62   $1,048.60   $1,048.60