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 $212.26   3.461%   $219.6063   $219.61   $219.60   $219.60  
  Purchase #2 $243.84   12.564%   $274.4761   $274.48   $274.50   $274.50  
  Purchase #3 $90.31   7.861%   $97.4093   $97.41   $97.40   $97.40  
  Purchase #4 $6.72   3.163%   $6.9326   $6.93   $6.95   $6.90  
  Purchase #5 $218.82   6.471%   $232.9798   $232.98   $233.00   $233.00  
  Purchase #6 $160.54   3.676%   $166.4415   $166.44   $166.45   $166.40  
  Purchase #7 $41.92   12.159%   $47.0171   $47.02   $47.00   $47.00  
  7 purchase totals = $974.41       $1,044.8627   $1,044.87   $1,044.90   $1,044.80