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	$198.42	8.538%	$215.3611	$215.36	$215.35	$215.40
Purchase #2	$89.65	11.447%	$99.9122	$99.91	$99.90	$99.90
Purchase #3	$80.89	12.369%	$90.8953	$90.90	$90.90	$90.90
Purchase #4	$133.39	7.610%	$143.541	$143.54	$143.55	$143.50
Purchase #5	$207.93	10.831%	$230.4509	$230.45	$230.45	$230.50
Purchase #6	$25.60	3.342%	$26.4556	$26.46	$26.45	$26.50
Purchase #7	$245.92	10.430%	$271.5695	$271.57	$271.55	$271.60
7 purchase totals =	$981.80		$1,078.1856	$1,078.19	$1,078.15	$1,078.30