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 $86.31   9.318%   $94.3524   $94.35   $94.35   $94.40  
  Purchase #2 $231.38   4.428%   $241.6255   $241.63   $241.65   $241.60  
  Purchase #3 $39.57   5.249%   $41.647   $41.65   $41.65   $41.60  
  Purchase #4 $119.65   7.802%   $128.9851   $128.99   $129.00   $129.00  
  Purchase #5 $190.97   10.747%   $211.4935   $211.49   $211.50   $211.50  
  Purchase #6 $60.62   3.262%   $62.5974   $62.60   $62.60   $62.60  
  Purchase #7 $226.41   11.370%   $252.1528   $252.15   $252.15   $252.20  
  7 purchase totals = $954.91       $1,032.8537   $1,032.86   $1,032.90   $1,032.90