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 $47.49   7.490%   $51.047   $51.05   $51.05   $51.00  
  Purchase #2 $250.59   13.586%   $284.6352   $284.64   $284.65   $284.60  
  Purchase #3 $41.99   9.460%   $45.9623   $45.96   $45.95   $46.00  
  Purchase #4 $170.58   7.869%   $184.0029   $184.00   $184.00   $184.00  
  Purchase #5 $119.28   3.140%   $123.0254   $123.03   $123.05   $123.00  
  Purchase #6 $237.93   5.503%   $251.0233   $251.02   $251.00   $251.00  
  Purchase #7 $190.41   11.791%   $212.8612   $212.86   $212.85   $212.90  
  7 purchase totals = $1,058.27       $1,152.5573   $1,152.56   $1,152.55   $1,152.50