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 $115.46   9.603%   $126.5476   $126.55   $126.55   $126.50  
  Purchase #2 $158.31   4.478%   $165.3991   $165.40   $165.40   $165.40  
  Purchase #3 $227.46   8.188%   $246.0844   $246.08   $246.10   $246.10  
  Purchase #4 $55.99   13.467%   $63.5302   $63.53   $63.55   $63.50  
  Purchase #5 $123.84   6.687%   $132.1212   $132.12   $132.10   $132.10  
  Purchase #6 $216.57   10.489%   $239.286   $239.29   $239.30   $239.30  
  Purchase #7 $47.58   12.598%   $53.5741   $53.57   $53.55   $53.60  
  7 purchase totals = $945.21       $1,026.5426   $1,026.54   $1,026.55   $1,026.50