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	$150.69	4.194%	$157.0099	$157.01	$157.00	$157.00
Purchase #2	$53.68	10.576%	$59.3572	$59.36	$59.35	$59.40
Purchase #3	$134.37	12.577%	$151.2697	$151.27	$151.25	$151.30
Purchase #4	$104.46	3.547%	$108.1652	$108.17	$108.15	$108.20
Purchase #5	$115.75	4.360%	$120.7967	$120.80	$120.80	$120.80
Purchase #6	$152.69	3.870%	$158.5991	$158.60	$158.60	$158.60
Purchase #7	$50.52	10.476%	$55.8125	$55.81	$55.80	$55.80
7 purchase totals =	$762.16		$811.0103	$811.02	$810.95	$811.10