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	$151.27	5.135%	$159.0377	$159.04	$159.05	$159.00
Purchase #2	$171.78	6.558%	$183.0453	$183.05	$183.05	$183.00
Purchase #3	$181.80	4.661%	$190.2737	$190.27	$190.25	$190.30
Purchase #4	$81.91	10.431%	$90.454	$90.45	$90.45	$90.50
Purchase #5	$103.94	13.670%	$118.1486	$118.15	$118.15	$118.10
Purchase #6	$185.56	9.744%	$203.641	$203.64	$203.65	$203.60
Purchase #7	$110.28	5.649%	$116.5097	$116.51	$116.50	$116.50
7 purchase totals =	$986.54		$1,061.1100	$1,061.11	$1,061.10	$1,061.00