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 $87.82   9.543%   $96.2007   $96.20   $96.20   $96.20  
  Purchase #2 $144.95   5.524%   $152.957   $152.96   $152.95   $153.00  
  Purchase #3 $79.87   3.246%   $82.4626   $82.46   $82.45   $82.50  
  Purchase #4 $240.50   9.237%   $262.715   $262.72   $262.70   $262.70  
  Purchase #5 $159.83   13.296%   $181.081   $181.08   $181.10   $181.10  
  Purchase #6 $44.62   6.842%   $47.6729   $47.67   $47.65   $47.70  
  Purchase #7 $190.74   8.799%   $207.5232   $207.52   $207.50   $207.50  
  7 purchase totals = $948.33       $1,030.6124   $1,030.61   $1,030.55   $1,030.70