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	$10.29	6.205%	$10.9285	$10.93	$10.95	$10.90
Purchase #2	$164.60	4.224%	$171.5527	$171.55	$171.55	$171.60
Purchase #3	$238.60	4.532%	$249.4134	$249.41	$249.40	$249.40
Purchase #4	$98.97	13.863%	$112.6902	$112.69	$112.70	$112.70
Purchase #5	$233.36	11.530%	$260.2664	$260.27	$260.25	$260.30
Purchase #6	$107.88	3.598%	$111.7615	$111.76	$111.75	$111.80
Purchase #7	$147.73	3.300%	$152.6051	$152.61	$152.60	$152.60
7 purchase totals =	$1,001.43		$1,069.2178	$1,069.22	$1,069.20	$1,069.30