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 $241.32   10.655%   $267.0326   $267.03   $267.05   $267.00  
  Purchase #2 $33.46   10.732%   $37.0509   $37.05   $37.05   $37.10  
  Purchase #3 $38.26   7.122%   $40.9849   $40.98   $41.00   $41.00  
  Purchase #4 $154.49   4.627%   $161.6383   $161.64   $161.65   $161.60  
  Purchase #5 $154.65   10.403%   $170.7382   $170.74   $170.75   $170.70  
  Purchase #6 $78.66   11.332%   $87.5738   $87.57   $87.55   $87.60  
  Purchase #7 $96.62   10.332%   $106.6028   $106.60   $106.60   $106.60  
  7 purchase totals = $797.46       $871.6215   $871.61   $871.65   $871.60