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	$164.72	8.538%	$178.7838	$178.78	$178.80	$178.80
Purchase #2	$80.91	11.365%	$90.1054	$90.11	$90.10	$90.10
Purchase #3	$87.58	8.116%	$94.688	$94.69	$94.70	$94.70
Purchase #4	$198.70	10.539%	$219.641	$219.64	$219.65	$219.60
Purchase #5	$147.83	10.248%	$162.9796	$162.98	$163.00	$163.00
Purchase #6	$61.25	8.194%	$66.2688	$66.27	$66.25	$66.30
Purchase #7	$235.55	5.739%	$249.0682	$249.07	$249.05	$249.10
7 purchase totals =	$976.54		$1,061.5348	$1,061.54	$1,061.55	$1,061.60