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 $36.26   13.156%   $41.0304   $41.03   $41.05   $41.00  
  Purchase #2 $180.90   13.378%   $205.1008   $205.10   $205.10   $205.10  
  Purchase #3 $15.33   8.177%   $16.5835   $16.58   $16.60   $16.60  
  Purchase #4 $241.31   4.347%   $251.7997   $251.80   $251.80   $251.80  
  Purchase #5 $228.52   13.195%   $258.6732   $258.67   $258.65   $258.70  
  Purchase #6 $201.50   4.763%   $211.0974   $211.10   $211.10   $211.10  
  Purchase #7 $219.47   10.395%   $242.2839   $242.28   $242.30   $242.30  
  7 purchase totals = $1,123.29       $1,226.5689   $1,226.56   $1,226.60   $1,226.60