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 $176.81   3.262%   $182.5775   $182.58   $182.60   $182.60  
  Purchase #2 $54.95   11.519%   $61.2797   $61.28   $61.30   $61.30  
  Purchase #3 $126.31   7.112%   $135.2932   $135.29   $135.30   $135.30  
  Purchase #4 $236.53   11.195%   $263.0095   $263.01   $263.00   $263.00  
  Purchase #5 $166.90   10.465%   $184.3661   $184.37   $184.35   $184.40  
  Purchase #6 $55.94   9.157%   $61.0624   $61.06   $61.05   $61.10  
  Purchase #7 $69.55   4.406%   $72.6144   $72.61   $72.60   $72.60  
  7 purchase totals = $886.99       $960.2028   $960.20   $960.20   $960.30