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 $224.37   7.611%   $241.4468   $241.45   $241.45   $241.40  
  Purchase #2 $152.85   10.596%   $169.046   $169.05   $169.05   $169.00  
  Purchase #3 $49.93   10.793%   $55.3189   $55.32   $55.30   $55.30  
  Purchase #4 $247.70   13.839%   $281.9792   $281.98   $282.00   $282.00  
  Purchase #5 $249.76   13.859%   $284.3742   $284.37   $284.35   $284.40  
  Purchase #6 $197.72   4.437%   $206.4928   $206.49   $206.50   $206.50  
  Purchase #7 $204.42   9.228%   $223.2839   $223.28   $223.30   $223.30  
  7 purchase totals = $1,326.75       $1,461.9418   $1,461.94   $1,461.95   $1,461.90