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	$215.97	3.262%	$223.0149	$223.01	$223.00	$223.00
Purchase #2	$106.51	11.414%	$118.6671	$118.67	$118.65	$118.70
Purchase #3	$56.25	11.179%	$62.5382	$62.54	$62.55	$62.50
Purchase #4	$27.70	9.417%	$30.3085	$30.31	$30.30	$30.30
Purchase #5	$63.67	3.397%	$65.8329	$65.83	$65.85	$65.80
Purchase #6	$73.52	6.436%	$78.2517	$78.25	$78.25	$78.30
Purchase #7	$91.68	9.155%	$100.0733	$100.07	$100.05	$100.10
7 purchase totals =	$635.30		$678.6866	$678.68	$678.65	$678.70