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 $141.96   6.746%   $151.5366   $151.54   $151.55   $151.50  
  Purchase #2 $225.75   11.689%   $252.1379   $252.14   $252.15   $252.10  
  Purchase #3 $10.38   7.790%   $11.1886   $11.19   $11.20   $11.20  
  Purchase #4 $86.90   6.307%   $92.3808   $92.38   $92.40   $92.40  
  Purchase #5 $191.78   7.488%   $206.1405   $206.14   $206.15   $206.10  
  Purchase #6 $181.64   12.534%   $204.4068   $204.41   $204.40   $204.40  
  Purchase #7 $87.69   9.838%   $96.3169   $96.32   $96.30   $96.30  
  7 purchase totals = $926.10       $1,014.1081   $1,014.12   $1,014.15   $1,014.00