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 $191.26   12.250%   $214.6894   $214.69   $214.70   $214.70  
  Purchase #2 $223.88   7.819%   $241.3852   $241.39   $241.40   $241.40  
  Purchase #3 $228.70   3.679%   $237.1139   $237.11   $237.10   $237.10  
  Purchase #4 $215.44   12.294%   $241.9262   $241.93   $241.95   $241.90  
  Purchase #5 $64.59   9.390%   $70.655   $70.66   $70.65   $70.70  
  Purchase #6 $238.44   3.763%   $247.4125   $247.41   $247.40   $247.40  
  Purchase #7 $212.34   8.373%   $230.1192   $230.12   $230.10   $230.10  
  7 purchase totals = $1,374.65       $1,483.3014   $1,483.31   $1,483.30   $1,483.30