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	$242.34	11.255%	$269.6154	$269.62	$269.60	$269.60
Purchase #2	$70.90	10.518%	$78.3573	$78.36	$78.35	$78.40
Purchase #3	$148.48	8.857%	$161.6309	$161.63	$161.65	$161.60
Purchase #4	$200.64	5.626%	$211.928	$211.93	$211.95	$211.90
Purchase #5	$103.74	7.689%	$111.7166	$111.72	$111.70	$111.70
Purchase #6	$246.36	4.113%	$256.4928	$256.49	$256.50	$256.50
Purchase #7	$207.29	7.768%	$223.3923	$223.39	$223.40	$223.40
7 purchase totals =	$1,219.75		$1,313.1333	$1,313.14	$1,313.15	$1,313.10