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	$119.40	3.549%	$123.6375	$123.64	$123.65	$123.60
Purchase #2	$90.45	12.347%	$101.6179	$101.62	$101.60	$101.60
Purchase #3	$197.69	10.571%	$218.5878	$218.59	$218.60	$218.60
Purchase #4	$209.85	8.462%	$227.6075	$227.61	$227.60	$227.60
Purchase #5	$194.71	7.555%	$209.4203	$209.42	$209.40	$209.40
Purchase #6	$152.55	4.337%	$159.1661	$159.17	$159.15	$159.20
Purchase #7	$206.96	10.826%	$229.3655	$229.37	$229.35	$229.40
7 purchase totals =	$1,171.61		$1,269.4026	$1,269.42	$1,269.35	$1,269.40