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 $34.52   3.368%   $35.6826   $35.68   $35.70   $35.70  
  Purchase #2 $235.69   13.848%   $268.3284   $268.33   $268.35   $268.30  
  Purchase #3 $104.54   5.132%   $109.905   $109.91   $109.90   $109.90  
  Purchase #4 $8.70   12.363%   $9.7756   $9.78   $9.80   $9.80  
  Purchase #5 $201.68   5.239%   $212.246   $212.25   $212.25   $212.20  
  Purchase #6 $167.29   5.469%   $176.4391   $176.44   $176.45   $176.40  
  Purchase #7 $122.80   8.342%   $133.044   $133.04   $133.05   $133.00  
  7 purchase totals = $875.22       $945.4207   $945.43   $945.50   $945.30