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 $228.25   7.767%   $245.9782   $245.98   $246.00   $246.00  
  Purchase #2 $207.46   3.201%   $214.1008   $214.10   $214.10   $214.10  
  Purchase #3 $79.52   6.815%   $84.9393   $84.94   $84.95   $84.90  
  Purchase #4 $73.77   3.794%   $76.5688   $76.57   $76.55   $76.60  
  Purchase #5 $30.30   8.821%   $32.9728   $32.97   $32.95   $33.00  
  Purchase #6 $150.29   11.563%   $167.668   $167.67   $167.65   $167.70  
  Purchase #7 $175.72   9.221%   $191.9231   $191.92   $191.90   $191.90  
  7 purchase totals = $945.31       $1,014.1510   $1,014.15   $1,014.10   $1,014.20