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 $167.84   4.296%   $175.0504   $175.05   $175.05   $175.10  
  Purchase #2 $208.45   10.653%   $230.6562   $230.66   $230.65   $230.70  
  Purchase #3 $23.75   5.832%   $25.1351   $25.14   $25.15   $25.10  
  Purchase #4 $62.85   7.476%   $67.5487   $67.55   $67.55   $67.50  
  Purchase #5 $209.93   7.341%   $225.341   $225.34   $225.35   $225.30  
  Purchase #6 $147.38   4.439%   $153.9222   $153.92   $153.90   $153.90  
  Purchase #7 $197.37   4.320%   $205.8964   $205.90   $205.90   $205.90  
  7 purchase totals = $1,017.57       $1,083.5500   $1,083.56   $1,083.55   $1,083.50