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	$221.46	12.679%	$249.5389	$249.54	$249.55	$249.50
Purchase #2	$143.45	7.245%	$153.843	$153.84	$153.85	$153.80
Purchase #3	$162.94	4.326%	$169.9888	$169.99	$170.00	$170.00
Purchase #4	$213.86	9.341%	$233.8367	$233.84	$233.85	$233.80
Purchase #5	$177.60	10.624%	$196.4682	$196.47	$196.45	$196.50
Purchase #6	$100.88	6.801%	$107.7408	$107.74	$107.75	$107.70
Purchase #7	$56.94	4.711%	$59.6224	$59.62	$59.60	$59.60
7 purchase totals =	$1,077.13		$1,171.0388	$1,171.04	$1,171.05	$1,170.90