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	$191.83	8.472%	$208.0818	$208.08	$208.10	$208.10
Purchase #2	$215.77	4.740%	$225.9975	$226.00	$226.00	$226.00
Purchase #3	$118.89	7.139%	$127.3776	$127.38	$127.40	$127.40
Purchase #4	$84.50	6.805%	$90.2502	$90.25	$90.25	$90.30
Purchase #5	$69.50	7.777%	$74.905	$74.91	$74.90	$74.90
Purchase #6	$41.69	4.760%	$43.6744	$43.67	$43.65	$43.70
Purchase #7	$39.84	9.800%	$43.7443	$43.74	$43.75	$43.70
7 purchase totals =	$762.02		$814.0308	$814.03	$814.05	$814.10