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	$105.80	10.153%	$116.5419	$116.54	$116.55	$116.50
Purchase #2	$179.44	3.534%	$185.7814	$185.78	$185.80	$185.80
Purchase #3	$223.51	6.501%	$238.0404	$238.04	$238.05	$238.00
Purchase #4	$106.78	5.491%	$112.6433	$112.64	$112.65	$112.60
Purchase #5	$147.49	6.180%	$156.6049	$156.60	$156.60	$156.60
Purchase #6	$121.80	12.361%	$136.8557	$136.86	$136.85	$136.90
Purchase #7	$192.90	7.617%	$207.5932	$207.59	$207.60	$207.60
7 purchase totals =	$1,077.72		$1,154.0608	$1,154.05	$1,154.10	$1,154.00