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	$167.64	7.548%	$180.2935	$180.29	$180.30	$180.30
Purchase #2	$82.96	9.170%	$90.5674	$90.57	$90.55	$90.60
Purchase #3	$118.87	3.613%	$123.1648	$123.16	$123.15	$123.20
Purchase #4	$93.92	12.442%	$105.6055	$105.61	$105.60	$105.60
Purchase #5	$215.49	13.503%	$244.5876	$244.59	$244.60	$244.60
Purchase #6	$112.70	12.771%	$127.0929	$127.09	$127.10	$127.10
Purchase #7	$43.88	5.127%	$46.1297	$46.13	$46.15	$46.10
7 purchase totals =	$835.46		$917.4414	$917.44	$917.45	$917.50