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	$143.41	8.677%	$155.8537	$155.85	$155.85	$155.90
Purchase #2	$76.38	9.303%	$83.4856	$83.49	$83.50	$83.50
Purchase #3	$238.91	13.615%	$271.4376	$271.44	$271.45	$271.40
Purchase #4	$232.92	12.865%	$262.8852	$262.89	$262.90	$262.90
Purchase #5	$154.42	8.697%	$167.8499	$167.85	$167.85	$167.80
Purchase #6	$51.72	5.657%	$54.6458	$54.65	$54.65	$54.60
Purchase #7	$175.76	5.692%	$185.7643	$185.76	$185.75	$185.80
7 purchase totals =	$1,073.52		$1,181.9221	$1,181.93	$1,181.95	$1,181.90