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	$78.70	11.347%	$87.6301	$87.63	$87.65	$87.60
Purchase #2	$126.67	11.202%	$140.8596	$140.86	$140.85	$140.90
Purchase #3	$158.48	9.268%	$173.1679	$173.17	$173.15	$173.20
Purchase #4	$181.33	10.178%	$199.7858	$199.79	$199.80	$199.80
Purchase #5	$198.32	13.685%	$225.4601	$225.46	$225.45	$225.50
Purchase #6	$181.64	5.354%	$191.365	$191.37	$191.35	$191.40
Purchase #7	$89.55	4.116%	$93.2359	$93.24	$93.25	$93.20
7 purchase totals =	$1,014.69		$1,111.5044	$1,111.52	$1,111.50	$1,111.60