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 $183.74   11.399%   $204.6845   $204.68   $204.70   $204.70  
  Purchase #2 $188.47   7.346%   $202.315   $202.32   $202.30   $202.30  
  Purchase #3 $165.94   12.710%   $187.031   $187.03   $187.05   $187.00  
  Purchase #4 $211.56   4.572%   $221.2325   $221.23   $221.25   $221.20  
  Purchase #5 $238.46   7.302%   $255.8723   $255.87   $255.85   $255.90  
  Purchase #6 $245.32   7.479%   $263.6675   $263.67   $263.65   $263.70  
  Purchase #7 $161.28   6.174%   $171.2374   $171.24   $171.25   $171.20  
  7 purchase totals = $1,394.77       $1,506.0402   $1,506.04   $1,506.05   $1,506.00