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 $58.36   4.851%   $61.191   $61.19   $61.20   $61.20  
  Purchase #2 $249.67   13.372%   $283.0559   $283.06   $283.05   $283.10  
  Purchase #3 $167.96   4.735%   $175.9129   $175.91   $175.90   $175.90  
  Purchase #4 $110.55   11.635%   $123.4125   $123.41   $123.40   $123.40  
  Purchase #5 $6.35   8.647%   $6.8991   $6.90   $6.90   $6.90  
  Purchase #6 $249.99   10.319%   $275.7865   $275.79   $275.80   $275.80  
  Purchase #7 $202.30   7.756%   $217.9904   $217.99   $218.00   $218.00  
  7 purchase totals = $1,045.18       $1,144.2483   $1,144.25   $1,144.25   $1,144.30