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 $56.49   10.286%   $62.3006   $62.30   $62.30   $62.30  
  Purchase #2 $94.57   10.337%   $104.3457   $104.35   $104.35   $104.30  
  Purchase #3 $224.51   4.355%   $234.2874   $234.29   $234.30   $234.30  
  Purchase #4 $212.68   5.458%   $224.2881   $224.29   $224.30   $224.30  
  Purchase #5 $195.77   8.415%   $212.244   $212.24   $212.25   $212.20  
  Purchase #6 $139.83   5.683%   $147.7765   $147.78   $147.80   $147.80  
  Purchase #7 $43.41   10.656%   $48.0358   $48.04   $48.05   $48.00  
  7 purchase totals = $967.26       $1,033.2781   $1,033.29   $1,033.35   $1,033.20