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 $59.76   5.194%   $62.8639   $62.86   $62.85   $62.90  
  Purchase #2 $190.96   11.299%   $212.5366   $212.54   $212.55   $212.50  
  Purchase #3 $22.44   7.808%   $24.1921   $24.19   $24.20   $24.20  
  Purchase #4 $98.74   12.215%   $110.8011   $110.80   $110.80   $110.80  
  Purchase #5 $204.30   7.601%   $219.8288   $219.83   $219.85   $219.80  
  Purchase #6 $136.85   5.419%   $144.2659   $144.27   $144.25   $144.30  
  Purchase #7 $246.70   11.707%   $275.5812   $275.58   $275.60   $275.60  
  7 purchase totals = $959.75       $1,050.0696   $1,050.07   $1,050.10   $1,050.10