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 $63.65   6.774%   $67.9617   $67.96   $67.95   $68.00  
  Purchase #2 $179.69   9.140%   $196.1137   $196.11   $196.10   $196.10  
  Purchase #3 $180.31   12.694%   $203.1986   $203.20   $203.20   $203.20  
  Purchase #4 $27.34   7.602%   $29.4184   $29.42   $29.40   $29.40  
  Purchase #5 $73.67   12.422%   $82.8213   $82.82   $82.80   $82.80  
  Purchase #6 $213.43   8.809%   $232.231   $232.23   $232.25   $232.20  
  Purchase #7 $222.96   11.348%   $248.2615   $248.26   $248.25   $248.30  
  7 purchase totals = $961.05       $1,060.0062   $1,060.00   $1,059.95   $1,060.00