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	$214.27	10.277%	$236.2905	$236.29	$236.30	$236.30
Purchase #2	$56.38	5.788%	$59.6433	$59.64	$59.65	$59.60
Purchase #3	$70.32	10.662%	$77.8175	$77.82	$77.80	$77.80
Purchase #4	$195.46	5.604%	$206.4136	$206.41	$206.40	$206.40
Purchase #5	$97.94	4.321%	$102.172	$102.17	$102.15	$102.20
Purchase #6	$127.93	9.269%	$139.7878	$139.79	$139.80	$139.80
Purchase #7	$223.41	4.419%	$233.2825	$233.28	$233.30	$233.30
7 purchase totals =	$985.71		$1,055.4072	$1,055.40	$1,055.40	$1,055.40