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 $188.45   3.749%   $195.515   $195.52   $195.50   $195.50  
  Purchase #2 $128.88   5.470%   $135.9297   $135.93   $135.95   $135.90  
  Purchase #3 $123.29   5.502%   $130.0734   $130.07   $130.05   $130.10  
  Purchase #4 $113.43   4.170%   $118.16   $118.16   $118.15   $118.20  
  Purchase #5 $213.37   4.797%   $223.6054   $223.61   $223.60   $223.60  
  Purchase #6 $192.64   11.462%   $214.7204   $214.72   $214.70   $214.70  
  Purchase #7 $105.88   5.107%   $111.2873   $111.29   $111.30   $111.30  
  7 purchase totals = $1,065.94       $1,129.2912   $1,129.30   $1,129.25   $1,129.30