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 $162.46   12.432%   $182.657   $182.66   $182.65   $182.70  
  Purchase #2 $194.52   5.531%   $205.2789   $205.28   $205.30   $205.30  
  Purchase #3 $191.67   13.475%   $217.4975   $217.50   $217.50   $217.50  
  Purchase #4 $107.62   3.636%   $111.5331   $111.53   $111.55   $111.50  
  Purchase #5 $155.82   10.523%   $172.2169   $172.22   $172.20   $172.20  
  Purchase #6 $32.98   5.189%   $34.6913   $34.69   $34.70   $34.70  
  Purchase #7 $102.45   7.561%   $110.1962   $110.20   $110.20   $110.20  
  7 purchase totals = $947.52       $1,034.0709   $1,034.08   $1,034.10   $1,034.10