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	$133.87	13.213%	$151.5582	$151.56	$151.55	$151.60
Purchase #2	$71.31	12.206%	$80.0141	$80.01	$80.00	$80.00
Purchase #3	$161.78	9.247%	$176.7398	$176.74	$176.75	$176.70
Purchase #4	$35.59	12.833%	$40.1573	$40.16	$40.15	$40.20
Purchase #5	$230.55	11.339%	$256.6921	$256.69	$256.70	$256.70
Purchase #6	$38.57	7.673%	$41.5295	$41.53	$41.55	$41.50
Purchase #7	$243.34	10.734%	$269.4601	$269.46	$269.45	$269.50
7 purchase totals =	$915.01		$1,016.1511	$1,016.15	$1,016.15	$1,016.20