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	$118.87	3.679%	$123.2432	$123.24	$123.25	$123.20
Purchase #2	$50.31	6.552%	$53.6063	$53.61	$53.60	$53.60
Purchase #3	$142.68	9.179%	$155.7766	$155.78	$155.80	$155.80
Purchase #4	$158.29	13.245%	$179.2555	$179.26	$179.25	$179.30
Purchase #5	$237.29	9.345%	$259.4648	$259.46	$259.45	$259.50
Purchase #6	$104.73	5.723%	$110.7237	$110.72	$110.70	$110.70
Purchase #7	$131.86	12.359%	$148.1566	$148.16	$148.15	$148.20
7 purchase totals =	$944.03		$1,030.2267	$1,030.23	$1,030.20	$1,030.30