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	$206.62	4.718%	$216.3683	$216.37	$216.35	$216.40
Purchase #2	$152.96	9.104%	$166.8855	$166.89	$166.90	$166.90
Purchase #3	$159.45	4.675%	$166.9043	$166.90	$166.90	$166.90
Purchase #4	$47.32	12.663%	$53.3121	$53.31	$53.30	$53.30
Purchase #5	$209.37	7.359%	$224.7775	$224.78	$224.80	$224.80
Purchase #6	$5.94	5.495%	$6.2664	$6.27	$6.25	$6.30
Purchase #7	$213.38	10.851%	$236.5339	$236.53	$236.55	$236.50
7 purchase totals =	$995.04		$1,071.0480	$1,071.05	$1,071.05	$1,071.10