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	$23.26	8.734%	$25.2915	$25.29	$25.30	$25.30
Purchase #2	$74.96	4.565%	$78.3819	$78.38	$78.40	$78.40
Purchase #3	$238.84	13.127%	$270.1925	$270.19	$270.20	$270.20
Purchase #4	$148.72	4.491%	$155.399	$155.40	$155.40	$155.40
Purchase #5	$199.42	11.858%	$223.0672	$223.07	$223.05	$223.10
Purchase #6	$88.35	3.705%	$91.6234	$91.62	$91.60	$91.60
Purchase #7	$147.27	8.696%	$160.0766	$160.08	$160.10	$160.10
7 purchase totals =	$920.82		$1,004.0321	$1,004.03	$1,004.05	$1,004.10