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	$231.92	4.723%	$242.8736	$242.87	$242.85	$242.90
Purchase #2	$113.38	6.246%	$120.4617	$120.46	$120.45	$120.50
Purchase #3	$111.34	6.534%	$118.615	$118.62	$118.60	$118.60
Purchase #4	$67.25	13.783%	$76.5191	$76.52	$76.50	$76.50
Purchase #5	$74.75	10.801%	$82.8237	$82.82	$82.80	$82.80
Purchase #6	$37.74	13.325%	$42.7689	$42.77	$42.75	$42.80
Purchase #7	$234.44	13.636%	$266.4082	$266.41	$266.40	$266.40
7 purchase totals =	$870.82		$950.4702	$950.47	$950.35	$950.50