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	$162.45	13.813%	$184.8892	$184.89	$184.90	$184.90
Purchase #2	$88.60	12.387%	$99.5749	$99.57	$99.55	$99.60
Purchase #3	$64.43	12.771%	$72.6584	$72.66	$72.65	$72.70
Purchase #4	$130.32	9.729%	$142.9988	$143.00	$143.00	$143.00
Purchase #5	$98.92	4.683%	$103.5524	$103.55	$103.55	$103.60
Purchase #6	$206.41	13.571%	$234.4219	$234.42	$234.40	$234.40
Purchase #7	$226.59	3.714%	$235.0056	$235.01	$235.00	$235.00
7 purchase totals =	$977.72		$1,073.1012	$1,073.10	$1,073.05	$1,073.20