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	$220.25	4.249%	$229.6084	$229.61	$229.60	$229.60
Purchase #2	$140.28	6.481%	$149.3715	$149.37	$149.35	$149.40
Purchase #3	$115.39	6.680%	$123.0981	$123.10	$123.10	$123.10
Purchase #4	$113.91	4.378%	$118.897	$118.90	$118.90	$118.90
Purchase #5	$200.49	8.559%	$217.6499	$217.65	$217.65	$217.60
Purchase #6	$159.80	9.694%	$175.291	$175.29	$175.30	$175.30
Purchase #7	$57.86	6.506%	$61.6244	$61.62	$61.60	$61.60
7 purchase totals =	$1,007.98		$1,075.5403	$1,075.54	$1,075.50	$1,075.50