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 $148.52   4.873%   $155.7574   $155.76   $155.75   $155.80  
  Purchase #2 $249.73   6.746%   $266.5768   $266.58   $266.60   $266.60  
  Purchase #3 $165.54   7.733%   $178.3412   $178.34   $178.35   $178.30  
  Purchase #4 $237.71   5.734%   $251.3403   $251.34   $251.35   $251.30  
  Purchase #5 $98.59   8.471%   $106.9416   $106.94   $106.95   $106.90  
  Purchase #6 $228.64   13.752%   $260.0826   $260.08   $260.10   $260.10  
  Purchase #7 $232.79   6.375%   $247.6304   $247.63   $247.65   $247.60  
  7 purchase totals = $1,361.52       $1,466.6703   $1,466.67   $1,466.75   $1,466.60