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 $194.76   3.712%   $201.9895   $201.99   $202.00   $202.00  
  Purchase #2 $47.60   5.641%   $50.2851   $50.29   $50.30   $50.30  
  Purchase #3 $58.31   10.571%   $64.474   $64.47   $64.45   $64.50  
  Purchase #4 $171.83   6.347%   $182.7361   $182.74   $182.75   $182.70  
  Purchase #5 $198.86   12.844%   $224.4016   $224.40   $224.40   $224.40  
  Purchase #6 $169.32   3.518%   $175.2767   $175.28   $175.30   $175.30  
  Purchase #7 $130.53   13.226%   $147.7939   $147.79   $147.80   $147.80  
  7 purchase totals = $971.21       $1,046.9569   $1,046.96   $1,047.00   $1,047.00