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	$17.84	9.644%	$19.5605	$19.56	$19.55	$19.60
Purchase #2	$38.54	13.196%	$43.6257	$43.63	$43.65	$43.60
Purchase #3	$117.38	8.703%	$127.5956	$127.60	$127.60	$127.60
Purchase #4	$31.60	13.706%	$35.9311	$35.93	$35.95	$35.90
Purchase #5	$22.54	11.220%	$25.069	$25.07	$25.05	$25.10
Purchase #6	$103.91	11.708%	$116.0758	$116.08	$116.10	$116.10
Purchase #7	$112.70	3.334%	$116.4574	$116.46	$116.45	$116.50
7 purchase totals =	$444.51		$484.3151	$484.33	$484.35	$484.40