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	$203.95	9.152%	$222.6155	$222.62	$222.60	$222.60
Purchase #2	$182.89	7.473%	$196.5574	$196.56	$196.55	$196.60
Purchase #3	$51.46	10.509%	$56.8679	$56.87	$56.85	$56.90
Purchase #4	$53.48	9.757%	$58.698	$58.70	$58.70	$58.70
Purchase #5	$202.33	9.740%	$222.0369	$222.04	$222.05	$222.00
Purchase #6	$176.52	13.683%	$200.6732	$200.67	$200.65	$200.70
Purchase #7	$166.50	11.344%	$185.3878	$185.39	$185.40	$185.40
7 purchase totals =	$1,037.13		$1,142.8367	$1,142.85	$1,142.80	$1,142.90