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	$107.34	8.473%	$116.4349	$116.43	$116.45	$116.40
Purchase #2	$143.60	6.571%	$153.036	$153.04	$153.05	$153.00
Purchase #3	$122.79	3.743%	$127.386	$127.39	$127.40	$127.40
Purchase #4	$104.85	9.314%	$114.6157	$114.62	$114.60	$114.60
Purchase #5	$73.28	12.345%	$82.3264	$82.33	$82.35	$82.30
Purchase #6	$81.43	10.512%	$89.9899	$89.99	$90.00	$90.00
Purchase #7	$37.35	7.760%	$40.2484	$40.25	$40.25	$40.20
7 purchase totals =	$670.64		$724.0373	$724.05	$724.10	$723.90