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	$127.55	4.144%	$132.8357	$132.84	$132.85	$132.80
Purchase #2	$105.75	5.851%	$111.9374	$111.94	$111.95	$111.90
Purchase #3	$185.71	4.452%	$193.9778	$193.98	$194.00	$194.00
Purchase #4	$56.81	10.814%	$62.9534	$62.95	$62.95	$63.00
Purchase #5	$145.83	4.192%	$151.9432	$151.94	$151.95	$151.90
Purchase #6	$48.99	11.625%	$54.6851	$54.69	$54.70	$54.70
Purchase #7	$172.28	11.390%	$191.9027	$191.90	$191.90	$191.90
7 purchase totals =	$842.92		$900.2353	$900.24	$900.30	$900.20