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	$205.98	6.615%	$219.6056	$219.61	$219.60	$219.60
Purchase #2	$216.75	3.388%	$224.0935	$224.09	$224.10	$224.10
Purchase #3	$84.65	5.276%	$89.1161	$89.12	$89.10	$89.10
Purchase #4	$80.80	11.345%	$89.9668	$89.97	$89.95	$90.00
Purchase #5	$144.27	13.272%	$163.4175	$163.42	$163.40	$163.40
Purchase #6	$248.72	8.327%	$269.4309	$269.43	$269.45	$269.40
Purchase #7	$23.41	8.740%	$25.456	$25.46	$25.45	$25.50
7 purchase totals =	$1,004.58		$1,081.0864	$1,081.10	$1,081.05	$1,081.10