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 $67.78   7.663%   $72.974   $72.97   $72.95   $73.00  
  Purchase #2 $205.75   8.596%   $223.4363   $223.44   $223.45   $223.40  
  Purchase #3 $63.31   3.723%   $65.667   $65.67   $65.65   $65.70  
  Purchase #4 $231.91   11.443%   $258.4475   $258.45   $258.45   $258.40  
  Purchase #5 $175.70   6.273%   $186.7217   $186.72   $186.70   $186.70  
  Purchase #6 $84.45   11.305%   $93.9971   $94.00   $94.00   $94.00  
  Purchase #7 $107.35   5.186%   $112.9172   $112.92   $112.90   $112.90  
  7 purchase totals = $936.25       $1,014.1608   $1,014.17   $1,014.10   $1,014.10