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 $59.86   6.249%   $63.6007   $63.60   $63.60   $63.60  
  Purchase #2 $164.41   10.466%   $181.6172   $181.62   $181.60   $181.60  
  Purchase #3 $185.78   10.113%   $204.5679   $204.57   $204.55   $204.60  
  Purchase #4 $212.35   6.339%   $225.8109   $225.81   $225.80   $225.80  
  Purchase #5 $241.68   12.818%   $272.6585   $272.66   $272.65   $272.70  
  Purchase #6 $221.25   3.494%   $228.9805   $228.98   $229.00   $229.00  
  Purchase #7 $114.90   3.182%   $118.5561   $118.56   $118.55   $118.60  
  7 purchase totals = $1,200.23       $1,295.7918   $1,295.80   $1,295.75   $1,295.90