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 $183.44   6.291%   $194.9802   $194.98   $195.00   $195.00  
  Purchase #2 $164.55   3.422%   $170.1809   $170.18   $170.20   $170.20  
  Purchase #3 $111.93   11.181%   $124.4449   $124.44   $124.45   $124.40  
  Purchase #4 $224.78   9.754%   $246.705   $246.71   $246.70   $246.70  
  Purchase #5 $99.92   3.412%   $103.3293   $103.33   $103.35   $103.30  
  Purchase #6 $45.33   5.522%   $47.8331   $47.83   $47.85   $47.80  
  Purchase #7 $195.91   6.565%   $208.7715   $208.77   $208.75   $208.80  
  7 purchase totals = $1,025.86       $1,096.2449   $1,096.24   $1,096.30   $1,096.20