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 $65.46   13.451%   $74.265   $74.27   $74.25   $74.30  
  Purchase #2 $215.90   4.568%   $225.7623   $225.76   $225.75   $225.80  
  Purchase #3 $233.82   7.641%   $251.6862   $251.69   $251.70   $251.70  
  Purchase #4 $199.27   10.299%   $219.7928   $219.79   $219.80   $219.80  
  Purchase #5 $241.86   4.677%   $253.1718   $253.17   $253.15   $253.20  
  Purchase #6 $190.69   10.367%   $210.4588   $210.46   $210.45   $210.50  
  Purchase #7 $231.79   6.602%   $247.0928   $247.09   $247.10   $247.10  
  7 purchase totals = $1,378.79       $1,482.2297   $1,482.23   $1,482.20   $1,482.40