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 $178.58   9.188%   $194.9879   $194.99   $195.00   $195.00  
  Purchase #2 $191.87   8.339%   $207.87   $207.87   $207.85   $207.90  
  Purchase #3 $68.81   10.270%   $75.8768   $75.88   $75.90   $75.90  
  Purchase #4 $238.73   5.277%   $251.3278   $251.33   $251.35   $251.30  
  Purchase #5 $168.82   4.131%   $175.794   $175.79   $175.80   $175.80  
  Purchase #6 $36.36   4.233%   $37.8991   $37.90   $37.90   $37.90  
  Purchase #7 $60.70   5.261%   $63.8934   $63.89   $63.90   $63.90  
  7 purchase totals = $943.87       $1,007.6490   $1,007.65   $1,007.70   $1,007.70