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	$200.36	11.303%	$223.0067	$223.01	$223.00	$223.00
Purchase #2	$111.53	11.118%	$123.9299	$123.93	$123.95	$123.90
Purchase #3	$113.27	12.680%	$127.6326	$127.63	$127.65	$127.60
Purchase #4	$37.95	3.539%	$39.2931	$39.29	$39.30	$39.30
Purchase #5	$142.72	3.390%	$147.5582	$147.56	$147.55	$147.60
Purchase #6	$157.37	4.108%	$163.8348	$163.83	$163.85	$163.80
Purchase #7	$8.93	5.403%	$9.4125	$9.41	$9.40	$9.40
7 purchase totals =	$772.13		$834.6678	$834.66	$834.70	$834.60