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 $59.38   7.254%   $63.6874   $63.69   $63.70   $63.70  
  Purchase #2 $82.62   10.842%   $91.5777   $91.58   $91.60   $91.60  
  Purchase #3 $98.44   8.205%   $106.517   $106.52   $106.50   $106.50  
  Purchase #4 $205.95   9.725%   $225.9786   $225.98   $226.00   $226.00  
  Purchase #5 $147.74   7.264%   $158.4718   $158.47   $158.45   $158.50  
  Purchase #6 $232.63   11.213%   $258.7148   $258.71   $258.70   $258.70  
  Purchase #7 $105.90   3.607%   $109.7198   $109.72   $109.70   $109.70  
  7 purchase totals = $932.66       $1,014.6671   $1,014.67   $1,014.65   $1,014.70