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	$146.82	5.429%	$154.7909	$154.79	$154.80	$154.80
Purchase #2	$110.54	3.413%	$114.3127	$114.31	$114.30	$114.30
Purchase #3	$190.27	10.652%	$210.5376	$210.54	$210.55	$210.50
Purchase #4	$116.28	5.354%	$122.5056	$122.51	$122.50	$122.50
Purchase #5	$105.35	6.812%	$112.5264	$112.53	$112.55	$112.50
Purchase #6	$165.35	9.219%	$180.5936	$180.59	$180.60	$180.60
Purchase #7	$100.93	10.627%	$111.6558	$111.66	$111.65	$111.70
7 purchase totals =	$935.54		$1,006.9226	$1,006.93	$1,006.95	$1,006.90