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 $45.46   7.666%   $48.945   $48.95   $48.95   $48.90  
  Purchase #2 $225.36   8.515%   $244.5494   $244.55   $244.55   $244.50  
  Purchase #3 $96.64   4.547%   $101.0342   $101.03   $101.05   $101.00  
  Purchase #4 $162.96   9.638%   $178.6661   $178.67   $178.65   $178.70  
  Purchase #5 $112.37   4.841%   $117.8098   $117.81   $117.80   $117.80  
  Purchase #6 $183.72   9.432%   $201.0485   $201.05   $201.05   $201.00  
  Purchase #7 $140.69   7.712%   $151.54   $151.54   $151.55   $151.50  
  7 purchase totals = $967.20       $1,043.5930   $1,043.60   $1,043.60   $1,043.40