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 $43.36   7.567%   $46.6411   $46.64   $46.65   $46.60  
  Purchase #2 $71.31   11.134%   $79.2497   $79.25   $79.25   $79.20  
  Purchase #3 $179.52   10.439%   $198.2601   $198.26   $198.25   $198.30  
  Purchase #4 $153.83   8.702%   $167.2163   $167.22   $167.20   $167.20  
  Purchase #5 $102.38   12.443%   $115.1191   $115.12   $115.10   $115.10  
  Purchase #6 $245.52   6.819%   $262.262   $262.26   $262.25   $262.30  
  Purchase #7 $167.92   9.832%   $184.4299   $184.43   $184.45   $184.40  
  7 purchase totals = $963.84       $1,053.1782   $1,053.18   $1,053.15   $1,053.10