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	$198.87	12.459%	$223.6472	$223.65	$223.65	$223.60
Purchase #2	$145.93	12.142%	$163.6488	$163.65	$163.65	$163.60
Purchase #3	$172.98	10.173%	$190.5773	$190.58	$190.60	$190.60
Purchase #4	$195.91	8.712%	$212.9777	$212.98	$213.00	$213.00
Purchase #5	$133.62	8.150%	$144.51	$144.51	$144.50	$144.50
Purchase #6	$38.62	9.121%	$42.1425	$42.14	$42.15	$42.10
Purchase #7	$215.82	13.387%	$244.7118	$244.71	$244.70	$244.70
7 purchase totals =	$1,101.75		$1,222.2153	$1,222.22	$1,222.25	$1,222.10