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 $148.82   12.627%   $167.6115   $167.61   $167.60   $167.60  
  Purchase #2 $138.77   12.563%   $156.2037   $156.20   $156.20   $156.20  
  Purchase #3 $54.64   12.281%   $61.3503   $61.35   $61.35   $61.40  
  Purchase #4 $200.92   3.514%   $207.9803   $207.98   $208.00   $208.00  
  Purchase #5 $225.27   9.308%   $246.2381   $246.24   $246.25   $246.20  
  Purchase #6 $108.91   13.318%   $123.4146   $123.41   $123.40   $123.40  
  Purchase #7 $200.64   5.871%   $212.4196   $212.42   $212.40   $212.40  
  7 purchase totals = $1,077.97       $1,175.2181   $1,175.21   $1,175.20   $1,175.20