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	$85.82	4.495%	$89.6776	$89.68	$89.70	$89.70
Purchase #2	$144.92	7.425%	$155.6803	$155.68	$155.70	$155.70
Purchase #3	$225.70	13.208%	$255.5105	$255.51	$255.50	$255.50
Purchase #4	$52.44	8.138%	$56.7076	$56.71	$56.70	$56.70
Purchase #5	$242.91	3.669%	$251.8224	$251.82	$251.80	$251.80
Purchase #6	$86.80	3.578%	$89.9057	$89.91	$89.90	$89.90
Purchase #7	$154.91	9.311%	$169.3337	$169.33	$169.35	$169.30
7 purchase totals =	$993.50		$1,068.6378	$1,068.64	$1,068.65	$1,068.60