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 $219.46   7.600%   $236.139   $236.14   $236.15   $236.10  
  Purchase #2 $92.74   5.673%   $98.0011   $98.00   $98.00   $98.00  
  Purchase #3 $224.78   10.215%   $247.7413   $247.74   $247.75   $247.70  
  Purchase #4 $215.93   11.713%   $241.2219   $241.22   $241.20   $241.20  
  Purchase #5 $181.46   13.375%   $205.7303   $205.73   $205.75   $205.70  
  Purchase #6 $63.43   5.809%   $67.1146   $67.11   $67.10   $67.10  
  Purchase #7 $208.98   10.848%   $231.6502   $231.65   $231.65   $231.70  
  7 purchase totals = $1,206.78       $1,327.5984   $1,327.59   $1,327.60   $1,327.50