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 $236.61   11.534%   $263.9006   $263.90   $263.90   $263.90  
  Purchase #2 $86.30   12.229%   $96.8536   $96.85   $96.85   $96.90  
  Purchase #3 $163.55   8.781%   $177.9113   $177.91   $177.90   $177.90  
  Purchase #4 $241.47   3.830%   $250.7183   $250.72   $250.70   $250.70  
  Purchase #5 $33.46   12.624%   $37.684   $37.68   $37.70   $37.70  
  Purchase #6 $106.96   9.747%   $117.3854   $117.39   $117.40   $117.40  
  Purchase #7 $202.93   3.136%   $209.2939   $209.29   $209.30   $209.30  
  7 purchase totals = $1,071.28       $1,153.7471   $1,153.74   $1,153.75   $1,153.80