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 $81.58   13.481%   $92.5778   $92.58   $92.60   $92.60  
  Purchase #2 $214.90   4.695%   $224.9896   $224.99   $225.00   $225.00  
  Purchase #3 $187.33   4.546%   $195.846   $195.85   $195.85   $195.80  
  Purchase #4 $142.97   13.613%   $162.4325   $162.43   $162.45   $162.40  
  Purchase #5 $171.45   5.674%   $181.1781   $181.18   $181.20   $181.20  
  Purchase #6 $203.86   3.494%   $210.9829   $210.98   $211.00   $211.00  
  Purchase #7 $198.92   3.806%   $206.4909   $206.49   $206.50   $206.50  
  7 purchase totals = $1,201.01       $1,274.4978   $1,274.50   $1,274.60   $1,274.50