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	$249.32	5.194%	$262.2697	$262.27	$262.25	$262.30
Purchase #2	$45.67	9.282%	$49.9091	$49.91	$49.90	$49.90
Purchase #3	$134.32	10.105%	$147.893	$147.89	$147.90	$147.90
Purchase #4	$46.37	11.222%	$51.5736	$51.57	$51.55	$51.60
Purchase #5	$197.48	7.410%	$212.1133	$212.11	$212.10	$212.10
Purchase #6	$161.26	5.721%	$170.4857	$170.49	$170.50	$170.50
Purchase #7	$134.43	3.836%	$139.5867	$139.59	$139.60	$139.60
7 purchase totals =	$968.85		$1,033.8311	$1,033.83	$1,033.80	$1,033.90