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 $218.94   7.107%   $234.5001   $234.50   $234.50   $234.50  
  Purchase #2 $56.36   7.740%   $60.7223   $60.72   $60.70   $60.70  
  Purchase #3 $101.84   12.232%   $114.2971   $114.30   $114.30   $114.30  
  Purchase #4 $87.26   13.781%   $99.2853   $99.29   $99.30   $99.30  
  Purchase #5 $183.91   7.244%   $197.2324   $197.23   $197.25   $197.20  
  Purchase #6 $103.25   13.265%   $116.9461   $116.95   $116.95   $116.90  
  Purchase #7 $226.91   5.718%   $239.8847   $239.88   $239.90   $239.90  
  7 purchase totals = $978.47       $1,062.8680   $1,062.87   $1,062.90   $1,062.80