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	$177.65	10.732%	$196.7154	$196.72	$196.70	$196.70
Purchase #2	$13.61	4.669%	$14.2455	$14.25	$14.25	$14.20
Purchase #3	$203.52	9.738%	$223.3388	$223.34	$223.35	$223.30
Purchase #4	$46.59	11.384%	$51.8938	$51.89	$51.90	$51.90
Purchase #5	$249.69	7.304%	$267.9274	$267.93	$267.95	$267.90
Purchase #6	$45.87	12.286%	$51.5056	$51.51	$51.50	$51.50
Purchase #7	$68.49	6.511%	$72.9494	$72.95	$72.95	$72.90
7 purchase totals =	$805.42		$878.5759	$878.59	$878.60	$878.40